The eldest son of Sir Robert Long, 6th Baronet and his wife Emma Child, he succeeded his father as 7th Baronet on 10 February 1767, and inherited the family estates, including the manors of Draycot (Wiltshire) and Athelhampton (Dorset).
He was a member of the Wiltshire Militia, gaining the rank of Captain in 1759 and Major in 1769, and later formed the Draycot Troop of Yeomanry Cavalry.
In 1784 he inherited the estates of Wanstead, and Tylney Hall from his uncle John Tylney, 2nd Earl Tylney, and Sir James took the additional name of Tylney. He became a generous benefactor of public and private charities, living a modest and unassuming lifestyle.
In 1775 Long married firstly, Harriot, fourth daughter of Jacob Bouverie, 1st Viscount Folkestone. She died on 12 November 1777; there were no children from this marriage. He married secondly, in 1785, Catherine Sydney Windsor, daughter of Other Windsor, 4th Earl of Plymouth.
Sir James Tylney-Long died at his home, Draycot House on 29 November 1794. His wife, Lady Catherine died in 1823. Sir James' only son, also called James, was born two months before his father's death and became the 8th Baronet. A sickly child, he died on 14 September 1805 just short of his eleventh birthday, and the vast estates of the Long, Child and Tylney families devolved onto the eldest of the 7th Baronet's three daughters, Catherine. The Baronetcy became extinct and Catherine's disastrous marriage to William Pole-Tylney-Long-Wellesley, 4th Earl of Mornington saw the destruction of Wanstead House.
- Inheriting the Earth: The Long Family's 500 Year Reign in Wiltshire; Cheryl Nicol
- Hand of Fate. The History of the Longs, Wellesleys and the Draycot Estate in Wiltshire. Tim Couzens 2001 OCLC 49204947
- "TYLNEY LONG (formerly LONG), Sir James, 7th Bt. (1737-94), of Draycot Cerne, Wilts". History of Parliament Online. Retrieved 16 June 2017.
- WSA 190:1
- Draycot House, by Geraldine Roberts, accessed June 2017
|Parliament of Great Britain|
| Member of Parliament for Marlborough
With: Lord Brudenell 1762–1768
James Brudenell 1768–1780
The Earl of Courtown
| Member of Parliament for Devizes
With: Charles Garth 1765–1780
Henry Jones 1780–1784
Henry Addington 1784–1788
| Member of Parliament for Wiltshire
With: Ambrose Goddard
Henry Penruddocke Wyndham
|Baronetage of England|