Robert Stewart, Viscount Castlereagh
Robert Stewart, 2nd Marquess of Londonderry, KG, GCH, PC, PC (Ire) (18 June 1769 – 12 August 1822), usually known as Lord Castlereagh[n 1] (// KAR-sul-RAY), was an Anglo-Irish British statesman. As British Foreign Secretary, from 1812 he was central to the management of the coalition that defeated Napoleon and was the principal British diplomat at the Congress of Vienna. Castlereagh was also leader of the British House of Commons in the Liverpool government from 1812 until his suicide in August 1822. Early in his career, as Chief Secretary for Ireland, he was involved in putting down the Irish Rebellion of 1798 and was instrumental in securing the passage of the Irish Act of Union of 1800.
His foreign policy from 1814 was to work with the leaders represented at the Congress of Vienna to provide a peace in Europe consistent with the conservative mood of the day. Much more than prime minister Lord Liverpool, he was responsible for the repressive domestic measures. Historian Charles Webster concludes:
- "There probably never was a statesman whose ideas were so right and whose attitude to public opinion was so wrong. Such disparity between the grasp of ends and the understanding of means amounts to a failure in statesmanship."
- 1 Title
- 2 Family
- 3 Early life and career
- 4 Chief Secretary for Ireland
- 5 At Westminster and in Government
- 6 The duel with Canning
- 7 Diplomatic career
- 8 Decline and death
- 9 Ghost story
- 10 Styles
- 11 Notes
- 12 References
- 13 Further reading
- 14 External links
Robert Stewart acquired the courtesy title Viscount Castlereagh in 1796 when his father was created Earl of Londonderry in the Irish peerage. Upon his father's death in 1821, he succeeded as 2nd Marquess of Londonderry, a title to which his father had been raised in 1816. His younger half-brother, the soldier, politician and diplomat Charles Stewart (later Vane) succeeded him as 3rd Marquess of Londonderry.
Robert Stewart was born in Henry Street, Dublin, Ireland, in 1769 the son of Robert Stewart (1739–1821) of Newtownards and Comber in County Down, with properties in Counties Donegal and Londonderry. The family seat was Mount Stewart, County Down.
The elder Stewart was an Irish politician and prominent Ulster landowner[n 2] He was created Baron Londonderry in 1789, Viscount Castlereagh in 1795, and Earl of Londonderry in 1796 by King George III. In 1771 he was elected in the Whig interest to the Irish House of Commons, where he was a supporter of Lord Charlemont and his allies who called for greater independence from Britain. From the Act of Union of 1800, however, he sat in the British House of Lords as an Irish representative peer. In 1816 he was created Marquess of Londonderry by the Prince Regent.
Stewart's mother, who died in childbirth when he was a year old, was Lady Sarah Frances Seymour, daughter of Francis Seymour-Conway, 1st Marquess of Hertford (a former British Ambassador to France (1764–65) and Lord Lieutenant of Ireland (1765–66)) and Isabella Fitzroy, daughter of Charles FitzRoy, 2nd Duke of Grafton. His father remarried five years later to Frances Pratt, daughter of Charles Pratt, 1st Earl Camden (1714–94), a leading English jurist and prominent political supporter of both the 1st Earl of Chatham and his son, William Pitt the Younger. Through the elder Stewart's marriages, he linked his family with the upper ranks of English nobility and political elites. The Camden connection was to be especially important for the political careers of both him and his elder son. By Frances Pratt, Stewart's father had three children who survived to adulthood, including Stewart's half-brother, Charles William Stewart (later Vane), Baron Stewart of Stewart's Court and Ballylawn in County Donegal (1814) and 3rd Marquess of Londonderry (1822).
In 1794, Stewart married Amelia (Emily) Hobart a daughter of John Hobart, 2nd Earl of Buckinghamshire, a former British Ambassador to Russia (1762–65) and Lord Lieutenant of Ireland (1776–80). Her mother, Caroline Conolly, was the granddaughter of William Conolly, Speaker of the Irish House of Commons in the early 18th century and one of the wealthiest landowners in Ireland. Caroline's brother, Thomas Conolly, was married to Louisa Lennox, sister of Emily FitzGerald, Duchess of Leinster, whose son and Emily's cousin-by-marriage, the aristocratic rebel Lord Edward FitzGerald, was a leader of the United Irishmen and one of their martyrs in the early stages of the Irish Rebellion of 1798.
Emily Stewart was well known as a hostess for her husband in both Ireland and London and during some of his most important diplomatic missions. In later years she was a leader of Regency London high society as one of the Lady Patronesses of Almack's. She is noted in contemporary accounts for her attractiveness, volubility and eccentricities. By all accounts, the two remained devoted to each other to the end, but they had no children.[n 3] The couple did, however, care for the young Frederick Stewart, while his father, Stewart's half-brother, Charles, was serving in the army.
Early life and career
Stewart had recurring health problems throughout his childhood, and his family elected to send him to The Royal School, Armagh, rather than to England for his secondary education. At the encouragement of Earl Camden, who took a great interest in him and treated him as a grandson by blood, he later attended St. John's College, Cambridge (1786–87), where he applied himself with greater diligence than expected from an aristocrat and obtained first class in his last examinations. He left Cambridge due to an extended illness, and after returning to Ireland did not pursue further formal education.
In 1790, Stewart was elected as a Member of the Irish Parliament for Down in one of the most expensive elections in Irish history.[n 4] Though for a time he was associated with the Northern Whig Club, he entered the Irish House of Commons as an Independent. He ran on a platform supporting Whig principles of electoral reform and opposing the Irish policies of the British Government. But even from the outset of his career, he was a personal supporter of the Prime Minister, William Pitt. Stewart was a lifelong advocate of Catholic concessions, though his position on the specific issue of Catholic Emancipation varied depending on his assessment of the potential repercussions on other policy priorities.
When war with France forced British Government attention on Ireland as a possible place of French invasion, the Irish Volunteers, seen as a potential source of disaffection, were disbanded by Dublin Castle, and a reorganised Militia was created in 1793. Stewart enrolled as an officer, a matter of course for a young Protestant aristocrat, and served as Lieutenant Colonel under the command of his wife's uncle, Thomas Conolly. Between Stewart's attendance to his militia duties, his pursuit of cultural, family and political interests in London, two trips to the Continent (in 1791, when he visited revolutionary Paris, and 1792), and the courtship of his wife whom he married in 1794, his life during this period was not centred on the activities of the Irish House of Commons, where he was listened to with respect but where he was not yet an important player. He was also beginning to disappoint some of his more radical original supporters in his constituency. As the French Revolution grew more bloody and Ireland more rebellious, Stewart increasingly worried about Ireland's future if the threats from France succeeded in breaking Ireland's links to Britain. He became further inclined to support not only Pitt personally but the British Government, even when he did not approve of a specific line taken in Irish policy.
In 1794, partly as a result of the promotion of Stewart's interests by his Camden connections, he was offered the Government-controlled seat of Tregony in Cornwall, where he was elected to the British House of Commons on a similar platform of reform principles and support for Pitt, on whose side he sat in Westminster. In 1796, he transferred to a seat for the Suffolk constituency of Orford, which was in the interest of his mother's family, the Seymour-Conways (Marquess of Hertford).
Chief Secretary for Ireland
In 1795, Pitt replaced the popular Lord Lieutenant of Ireland, Lord Fitzwilliam, with Stewart's uncle, the 2nd Earl Camden. Camden's arrival in Dublin was greeted with riots, and that year Stewart crossed the floor to join the supporters of the British Government.[n 5] Stewart became an essential adviser to the inexperienced and unpopular Lord Lieutenant, who was Stewart's senior by only ten years.
In 1796, when the French invasion of Ireland failed at Bantry Bay due to bad weather and not to Ireland's military preparations or the British Navy, Castlereagh as a leader of the Militia saw first hand how ripe Ireland was for breaking from Britain and becoming another French satellite. Despairing of obtaining timely military support from Britain if Ireland were again threatened with invasion, for the next several years, he was increasingly involved in measures against those promoting a Rising, but his initial principles of reform and emancipation continued to hold a place in his political thought.
In 1797, Castlereagh was at last appointed to office, as Keeper of the King's Signet for Ireland.[n 6] As martial law was declared in the face of growing turmoil, he was made both a Lord of the Treasury and a Member of the Privy Council of Ireland (1797–1800).[n 7] At the urging of Camden, Castlereagh assumed many of the onerous duties of the often-absent Chief Secretary for Ireland who was responsible for day-to-day administration and asserting the influence of Dublin Castle in the House of Commons. [n 8] In this capacity, and after March 1798 as Acting Chief Secretary, Castlereagh played a key role in crushing the Irish Rebellion of 1798, offering clemency to commoners who had supported the rebellion, and focusing instead on pursuing rebel leaders.
In 1799, in furtherance of both his own political vision and Pitt's policies, Castlereagh began lobbying in the Irish and British Parliaments for an official union between the two, convinced that it was the best way to soothe the long-standing divides in Ireland, insulate Ireland from further radical disaffection, and protect Britain from French military threats via Ireland. His first attempt, at the opening of the Irish session of 1799, met with failure during long, heated debates. A year of further intense preparation followed, with an impressive display of Machiavellian tactics that included the common practice of bribery through peerages, honours and money, but bribery on a truly uncommon scale. In the summer of 1800, Castlereagh together with the Lord Lieutenant, Marquess Cornwallis, finally succeeded in steering the Irish Act of Union through both Parliaments.
During the campaign for the Act of Union, both Castlereagh and Cornwallis had, in good faith, forwarded informal assurances they had received from Pitt's Cabinet to the Irish Catholics that they would be allowed to sit in Parliament. Both Castlereagh and Cornwallis knew Catholic emancipation would be critical if their objectives for Union were to be realised. Emancipation was, however, opposed by much of the British establishment, including George III, who was convinced that it would violate his royal oath as protector of the Protestant faith. Pitt tried to follow through on his commitment, but when it came to light that the King had approached Henry Addington, an opponent of Catholic emancipation, about becoming Prime Minister to replace the pro-emancipation Pitt, both Castlereagh and Pitt resigned in protest. Castlereagh would long be held personally responsible by many Catholics in Ireland for the breach of promise and the British Government's betrayal of their rights.
At Westminster and in Government
When the newly united Parliament of the United Kingdom met in 1801, Castlereagh took his seat in the House of Commons from his Down constituency. By 1802, tensions between Tories supporting emancipation and those opposing had relaxed, and Addington had obtained his desired cessation of hostilities with France (the Peace of Amiens). At a shift in the composition of Addington's Government, Castlereagh accepted the offer to enter the Cabinet as President of the Board of Control, where he mediated bitter disputes between the Governor-General of India, Richard Wellesley, and the Directors of the East India Company, smoothing quarrels while generally supporting Lord Wellesley's policies.
After the renewal of the war against Napoleon, at the urging of Castlereagh and other long-time supporters, in 1804 Pitt returned as Prime Minister, and Castlereagh was promoted to Secretary of State for War and the Colonies. As the only other member of Pitt's Government in the House of Commons, Castlereagh became Pitt's political deputy, taking on ever more burdens as Pitt's health continued to decline. After Pitt's death in 1806, Castlereagh resigned amid the chaos of the Ministry of All the Talents. When that Government collapsed, Castlereagh again became Secretary of State for War and the Colonies in 1807, this time in the ministry of the Duke of Portland.
The duel with Canning
As minister for War, he became involved in disputes with Foreign Secretary George Canning over the Walcheren Expedition and its failure. Canning saw it as a diversion of troops from the Peninsular War based on a hopeless plan. However, Castlereagh had the support of Lord Wellesley's younger brother General Arthur Wellesley (future Duke of Wellington), and evidence later surfaced that Canning himself had interfered with the plan, selecting the Earl of Chatham to command the expedition. The Portland government became increasingly paralysed by disputes between the two men. Portland was in deteriorating health and gave no lead, until Canning threatened resignation unless Castlereagh was removed and replaced by Lord Wellesley. Wellesley himself was neither complicit with nor even aware of the arrangement, but Portland secretly agreed to make this change when it became possible.
Castlereagh discovered the deal in September 1809 and demanded redress. He challenged Canning to a duel, which Canning accepted. Canning had never before fired a pistol. The duel was fought on 21 September 1809 on Putney Heath. Canning missed but Castlereagh wounded his opponent in the thigh. There was much outrage that two cabinet ministers had resorted to such a method, and they both felt compelled to resign from the government. Six months later, Canning published a full account of his actions in the affair, and many who had initially rallied to him[who?] became convinced Castlereagh had been betrayed by his cabinet colleague.
Three years later, in 1812, Castlereagh returned to the government, this time as Foreign Secretary, a role in which he served for the next ten years. He also became leader of the House of Commons in the wake of Spencer Perceval's assassination in 1812.
Treaty of Chaumont
In his role of Foreign Secretary he was instrumental in negotiating what has become known as the quadruple alliance between Britain, Austria, Russia, and Prussia at Chaumont in March 1814, in the negotiation of the Treaty of Paris that brought peace with France, and at the Congress of Vienna. The Treaty of Chaumont was part of the final deal offered to Napoleon Bonaparte in 1814. Napoleon rejected it and it never took effect. However, the key terms reaffirmed decisions that had been made already. These decisions were again ratified and put into effect by the Congress of Vienna of 1814–1815. The terms were largely written by Lord Castlereagh, who offered cash subsidies to keep the other armies in the field against Napoleon. Key terms included the establishment of a confederated Germany, the division into independent states, the restoration of the Bourbon kings of Spain, and the enlargement of Holland to include what in 1830 became modern Belgium. The treaty of Chaumont became the cornerstone of the European Alliance which formed the balance of power for decades.
Congress of Vienna
At the Congress of Vienna, Castlereagh designed and proposed a form of collective and collaborative security for Europe, then called a Congress system. In the Congress system, the main signatory powers met periodically (every two years or so) and collectively managed European affairs. This system was used in an attempt to address the Polish-Saxon crisis at Vienna and the question of Greek independence at Laibach. The following ten years saw five European Congresses where disputes were resolved with a diminishing degree of effectiveness. Finally, by 1822, the whole system had collapsed because of the irreconcilable differences of opinion among Britain, Austria, and Russia, and because of the lack of support for the Congress system in British public opinion. The Holy Alliance, which Castlereagh opposed, lingered for some time, however, and even had effects on the international stage as late as the Crimean war. The order created by the Congress of Vienna was also more successful than Congresses themselves, preventing major European land wars until the First World War a century later. Scholars and historians have seen the Congress system as a forerunner of the modern collective security, international unity, and cooperative agreements of NATO, the EU, the League of Nations, and the United Nations.
In the years 1812 to 1822, Castlereagh continued to manage Britain's foreign policy, generally pursuing a policy of continental engagement uncharacteristic of British foreign policy in the nineteenth century. Castlereagh was not known to be an effective public speaker and his diplomatic presentation style was at times abstruse. Henry Kissinger says he developed a reputation for integrity, consistency, and goodwill, which was perhaps unmatched by any diplomat of that era.
Decline and death
Despite his contributions to the defeat of Napoleon and restoration of peace, Castlereagh became extremely unpopular at home. He was attacked for his construction of a peace that gave a free hand to reactionary governments on the Continent to suppress dissent. He was also condemned for his association with repressive measures of the Home Secretary, Lord Sidmouth (the former Prime Minister Addington). As Leader of the House of Commons for the Liverpool Government, he was often called upon to defend government policy in the House. He had to support the widely reviled measures taken by Sidmouth and the others, including the infamous Six Acts, to remain in cabinet and continue his diplomatic work. For these reasons, Castlereagh appears with other members of Lord Liverpool's Cabinet in Shelley's poem The Masque of Anarchy, which was inspired by, and heavily critical of, the Peterloo massacre:
- I met Murder on the way –
- He had a mask like Castlereagh –
- Very smooth he looked, yet grim;
- Seven bloodhounds followed him
- All were fat; and well they might
- Be in admirable plight,
- For one by one, and two by two,
- He tossed them human hearts to chew
- Which from his wide cloak he drew.
After the death of his father in 1821, Castlereagh became the 2nd Marquess of Londonderry. As a non-representative Irish peer Londonderry was eligible to sit in the House of Commons though he had to leave his Irish seat and instead be elected to an English seat. In 1822, he began to suffer from a form of paranoia or a nervous breakdown, possibly as a result of an attack of gout combined with the stress of public criticism. He was also severely overworked with both his responsibilities in leading the government in the House and the never-ending diplomacy required to manage conflicts among the other major powers. At the time, he said "My mind, is, as it were, gone." Londonderry returned to his country seat at Loring Hall in Water Lane, North Cray, Kent on the advice of his doctor. On 9 August 1822 he had an audience with King George IV in which he appeared distracted and mentally disturbed. Among other surprising remarks he revealed to the King that he thought he was being blackmailed for homosexuality.[n 9]
On 12 August, although his wife had succeeded in removing razors from his possession and even though his doctor was in attendance, Castlereagh managed to find a pen knife with which he committed suicide by cutting his own throat.[n 10]
An inquest concluded that the act had been committed while insane, avoiding the harsh strictures of a felo de se verdict.[n 11] The verdict allowed Lady Londonderry to see her husband buried with honour in Westminster Abbey near his mentor, William Pitt. Some radicals, notably William Cobbett, claimed a "cover-up" within the government and viewed the verdict and Castlereagh's public funeral as a damning indictment of the elitism and privilege of the unreformed electoral system. His funeral on 20 August was greeted with jeering and insults along the processional route, although not to the level of unanimity projected in the radical press. A funeral monument was not erected until 1850 by his half-brother and successor, Charles Stewart Vane, 3rd Marquess of Londonderry.
Sometime after Castlereagh's death, Lord Byron wrote a savage quip about his grave:
- Posterity will ne'er survey
- A nobler grave than this:
- Here lie the bones of Castlereagh:
- Stop, traveller, and piss.
And yet, some of Castlereagh's political opponents were gracious in their epigrams. Henry Brougham, a Whig politician and later the Lord Chancellor, who had battled frequently with Castlereagh, once almost to the point of calling him out, and had denigrated his skills as Leader, wrote in the week following Castlereagh's death:
- Put all their other men together in one scale, and poor Castlereagh in the other – single he plainly weighed them down... One can't help feeling a little for him, after being pitted against him for several years, pretty regularly. It is like losing a connection suddenly. Also he was a gentleman, and the only one amongst them.
An English Heritage blue plaque is displayed at the entrance to the listed building Loring Hall, now a care facility for those with learning disabilities, in commemoration of Castlereagh, who occupied the property from 1811 until his death.
Robert Stewart was said to have seen a ghost in the barracks at Ballyshannon one night. He claimed that the face of a boy came out of the fireplace and approached him. When he stepped forward toward it, it receded and then faded away. Castlereagh supposedly told this story to Sir Walter Scott, and called the apparition "The Radiant Boy."
- Robert Stewart, Esquire (1769–1789)
- The Honourable Robert Stewart (1789–1796)
- Viscount Castlereagh (1796–1797)
- The Right Honourable Viscount Castlereagh (1797–1814)
- The Right Honourable Viscount Castlereagh, KG (1814–1821)
- The Most Honourable The Marquess of Londonderry, KG, GCH, PC, PC (Ire) (1821–1822)
- The name Castlereagh derives from the baronies of Castlereagh (or Castellrioughe) and Ards, in which the manors of Newtownards and Comber were located. The estates included the demesne land of Mount Pleasant, later Mount Stewart, which became the family seat of the Londonderrys. (See Leigh, Castlereagh, p. 15.)
- a nephew of Robert Cowan, a wealthy and successful Governor of Bombay for the British East India Company, whose heir was the elder Stewart's mother, Cowan's sister Mary. Much of the Stewart family wealth was based on the estates which came into the family through the Cowan inheritance, which put the family squarely in the landed gentry class of Ulster Presbyterians whose ancestors first arrived in Ireland during the Plantation of Ulster. (See "The Cowan Inheritance". Public Records Office of Northern Ireland. 7 September 2006. Archived from the original on 14 November 2007. Retrieved 6 July 2009.)
- In a profile of Castlereagh published within months of his death, he was reported to have had, prior to his marriage, a son by a maidservant who lived near the Mount Stewart estate, and whom it was rumored he supported. (Dr. Felton Reede, Private Life of the Marquess of Londonderry, (1822), cited in Leigh, Castlereagh, pp 34 and 144.)
- The Down election of 1790 was fought against the elder Stewart's rival for influence in Ulster, Wills Hill, 1st Marquess of Downshire, who controlled both Down seats. The elder Stewart, who had been raised to the Irish peerage the previous year and was thereby ineligible, persed his son to stand for the seat, though his son would not himself be eligible until he turned twenty-one after the election but before the opening of the next session. His son was backed, as he had been, by Whigs and Dissenters. The election expenses to the Stewarts reached the extraordinary sum of £60,000, financed by a mortgage of Mount Stewart, which Castlereagh's father spent much of the next decades paying off. (See Leigh, Castlereagh.)
- The war with France absorbed much of the attention of Government and Parliament, and what attention was paid to an increasingly radicalised Ireland was confused and inconsistent. Pitt's dismissal of the popular Lord Fitzwilliam in 1795, over Fitzwilliam's aggressive support of Whig patronage and Catholic emancipation, produced outrage and rioting in Dublin. Castlereagh had watched the unravelling of Irish policy with deep concern and knew what sort of reaction to expect to Fitzwilliam's dismissal. But he was in no position to steer Irish policy nor could he object to the inevitable departure of Fitzwilliam, especially as the person appointed to replace Fitzwilliam was the brother of Stewart's step-mother, John Jeffreys Pratt, who had recently succeed as 2nd Earl Camden. (See Leigh, Castlereagh, Ch. 3.)
- Castlereagh had been re-elected without opposition from Down in 1797 and continued to hold this seat while in office in Ireland. He could not continue to hold both Irish office and the seat in Westminster for Orford, which he therefore resigned. (See Leigh, Castlereagh, Ch 4.) In the Irish election of 1798, he stood for Newtown Limavady as well as for Down. He was successful for both constituencies and chose to sit for the latter.
- In Council, though he was active in pursuing plots against the Government, he countered the influence of the more extreme members of the Protestant Ascendancy who, against especially the policies of the new Commander-in-Chief for Ireland, Sir Ralph Abercromby, called for indiscriminate violence to suppress all threat of rebellion. (See Leigh, Castlereagh, Ch 4).
- The Chief Secretary for Ireland from 1795–98 was Thomas Pelham, but he was continually absent from his duties due to illness. Camden pressed London to replace Pelham, recommending in his stead Castlereagh, whose performance in office was admired by those in London concerned with Irish policy. But as an example of the perverse prejudices of the era, Castlereagh, who might have been especially competent in this delicate and demanding office because he was an Irishman, was also ineligible to represent the Crown in Ireland because he was an Irishman, even though this Irishman was grandson of an English Marquess, great-grandson of an English Duke and son-in-law of an English Earl. After pressure by Pitt on George III who shared the prejudice against appointments of Irish as representatives of the Crown in Ireland, Castlereagh was appointed Acting Chief Secretary in March 1798. But it was only in November 1798, after the Rebellion had been put down that, in response to imperious demands from the next influential Lord Lieutenant, Marquess Cornwallis, Castlereagh was given the permanent office, and for the first time the Chief Secretary for Ireland was an Irishman. The next month, Castlereagh was admitted to the King's Privy Council. (See Leigh, Castlereagh Ch 4, and PDF (112 KiB) 18 Dec 1798, p. 1 (1 page pdf).)
- In addition to the events surrounding the suicide itself, towards the end of his life there are increasing reports, both contemporaneous and in later memoirs, of exceptionally powerful rages and sudden bouts of uncharacteristic forgetfulness. At a 9 August meeting with the King, Castlereagh is reported to have been distracted, to have told the King he was being mysteriously watched by a servant, and to have said, "I am accused of the same crime as the Bishop of Clogher." Percy Jocelyn, who had been the Bishop of Clogher until the previous month, was prosecuted for homosexuality. (See H. Montgomery Hyde, Trials of Oscar Wilde, Courier Dover Publications, ISBN 0-486-20216-X.) The King surmised that Castlereagh believed he was being blackmailed for the same reason. It remains unclear whether there was some sort of extortion attempt, and if so, whether such attempt represented a real threat of exposure, or whether the purported blackmail was a symptom of paranoia he otherwise appeared to be displaying at the time. The King is said to have advised Castlereagh to consult a physician and, disturbed by the condition of his Foreign Secretary, shared his concerns with Castlereagh's friend, the Duke of Wellington. Wellington not only advised Castlereagh that he was suffering from delusions but sent a note to Castlereagh's doctor urging him to see his patient at the first opportunity. Wellington's note was submitted as evidence at the inquest. (See Leigh, Castlereagh, which draws extensively from memoirs of people who claimed to have observed Castlereagh's uncharacteristic behaviour, such as Dorothea, Countess de Lieven. The appendices include contemporary letters from observers and excerpts from the journal of Harriet Arbuthnot, who was a close friend of both Castlereagh and Wellington.)
- In a retrospective, and therefore necessarily speculative diagnosis, a thoughtful recent study has linked various instances of (at the time) little explained illness to syphilis, possibly contracted at Cambridge: here Stewart's undergraduate studies were interrupted by a mysterious illness first apparent during the closing months of 1787, and which kept him away from Cambridge through the summer of 1788. Later, there were unexplained illnesses in 1801 and 1807, the first described by a contemporary as "brain fever" which would be consistent with syphilitic meningitis. (See Giles Hunt, The Duel: Castlereagh, Canning and Deadly Cabinet Rivalry (2008).)
- Suicide was illegal in England until 1961. Prior to the Right to Burial Act of 1823, a suicide was denied a Christian burial and, until the Abolition of Forfeiture Act of 1870, his property was forfeited to the Crown. These cruel penalties were less and less frequently applied over the course of the 18th century, especially in the case of wealthier perpetrators. Inquests were likely to view suicide as itself evidence of the disturbed state of the perpetrator's mind. (See e.g., Clifton D. Bryant, Handbook of Death and Dying, Sage Publications (2003) pp. 316–17.)
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- Charles Webster, The Foreign Policy of Castlereagh (1931) P 231
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- Gregory Fremont-Barnes; Todd Fisher (2004). The Napoleonic Wars: The Rise and Fall of an Empire. Osprey Publishing. pp. 302–5.
- Frederick B. Artz, Reaction & Revolution: 1814–1832 (1934), p. 110
- Kissinger, Henry (1957). A World Restored: Metternich, Castlereagh and the Problems of Peace, 1812–22. London: Weidenfeld & Nicolson.
- "Register–Deaths". Blackwood's Magazine (Edinburgh: William Blackwood) 12: 520. October 1822. Retrieved 28 August 2011.
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- "Chapter 1 of Victorian Suicide: Mad Crimes and Sad Histories, Barbara T. Gates". Victorian Web. 6 June 2001. Retrieved 29 May 2009.
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- Sir Herbert Maxwell, ed. (1904), "Henry Brougham M.P. to Thomas Creevey, August 19, 1822," The Creevey Papers, London: John Murray, 2nd edition, Vol II, p 44. Internet Archive retrieved on 9 July 2009.
- "STEWART, ROBERT, VISCOUNT CASTLEREAGH (1769–1822)". English Heritage. Retrieved 22 October 2012.
- Graves, Alfred Perceval (1914). Irish Literary and Musical Studies. New York: Charles Scribner's Sons. p. 95.
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- List of the Knights of the Garter (1348–present) www.heraldica.org
- Bew, John. Castlereagh: Enlightenment, War and Tyranny, London: Quercus (2011) ISBN 978-0-85738-186-6
- review essay by Jack Gumpert Wasserman, in The Byron Journal (2013) Vol. 41, No. 1 online
- Bew, John. Castlereagh: A Life, Oxford: Oxford University Press (2012) ISBN 978-0-19993-159-0 online review
- Bartlett, Christopher John. Castlereagh, London: Macmillan (1966) — especially for diplomatic history
- Derry, John W. Castlereagh, London: A. Lane (1976)
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- Hunt, Giles. The Duel: Castlereagh, Canning and deadly cabinet rivalry, B Tauris & Co Ltd, UK/Palgrave Macmillan (2008) ISBN 1-84511-593-7
- Jarrett, Mark (2013). The Congress of Vienna and its Legacy: War and Great Power Diplomacy after Napoleon. London: I. B. Tauris & Company, Ltd. ISBN 978-1780761169.
- Lawrence, Thomas, and C. J. Bartlett. The Foreign Policy of Castlereagh, 1812-1815, Britain and the European Alliance (1925) online
- King, David. Vienna 1814; How the Conquerors of Napoleon Made Love, War, and Peace at the Congress of Vienna, Random House, Inc. (2008) ISBN 978-0-307-33716-0
- Henry Kissinger, A World Restored: Metternich, Castlereagh, and the Problems of Peace, 1812–22, Houghton Mifflin (1973) ISBN 978-0-395-17229-2 (1st pub.1957)
- Leigh, Ione. Castlereagh, London: Collins (1951) — especially for early years, access to family papers
- Muir, Rory. Britain and the defeat of Napoleon, 1807–1815, New Haven: Yale University Press (1966) ISBN 978-0-300-06443-8
- Harold Nicolson, The Congress of Vienna, Constable & Co Ltd, UK/Harcourt Brace and Company (1946)
- Perkins, Bradford. Castlereagh and Adams: England and the United States, 1812–1823, Berkeley: University of California Press (1964)
- Schroeder, Paul W. The Transformation of European Politics, 1763–1848 (1996), European diplomatic history online
- Webster, Charles. The Foreign Policy of Castlereagh, in 2 volumes, 1812–1815 (1931) and 1815–1822 (1925; 2nd ed 1934) vol 1 online
- Zamoyski, Adam. Rites of Peace; the Fall of Napoleon and the Congress of Vienna, HarperCollins Publishers (2007) ISBN 978-0-06-077518-6
Primary sources and older studies
- Memoirs and Correspondence of Viscount Castlereagh, 2nd Marquess of Londonderry, edited by his brother, Charles William (Stewart) Vane, 3rd Marquess of Londonderry, London: John Murray (1848–53) in 12 volumes
- Henry Lord Brougham, "Lord Castlereagh," Historical Sketches of Statesmen in the Time of George III, London: Charles Knight & Co. (1845), Second Series, Vol I, pp. 149–61
- Sir A. Alison., Lives of Lord Castlereagh and Sir Charles Stewart, 3 vols., London: Blackwood (1861)
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- Hansard 1803–2005: contributions in Parliament by Viscount Castlereagh
- A Letter to Lord Viscount Castlereagh, John C. Hobhouse, London: Robert Stodart (1819), on the Peterloo massacre
- Portraits of Robert Stewart, 2nd Marquess of Londonderry (Lord Castlereagh) at the National Portrait Gallery, London