He was born in Tupholme the extramarital son of a farmer and stockbreeder. He attended Horncastle Grammar School and was trained as a land surveyor. Unsatisfied with his job, he obtained a commission in the army at the age of 21. In January 1804 he married Jane Worsley but she died two years later giving birth to their first child. In 1808 he married Susan Wilkinson. He then quit his commission in the army and, with the help of his father, bought a farm. The farm was not a success and in 1811 he moved to London.
Beginning of revolutionary involvement
Travel in France and the United States of America exposed Thistlewood to revolutionary ideas. Shortly after his return to England, he joined the Society of Spencean Philanthropists in London. By 1816, Thistlewood had become a leader in the organisation, and was labelled a "dangerous character" by police.
On 2 December 1816 a mass meeting took place at Spa Fields. The Spenceans had planned to encourage rioting at this meeting and then seize control of the British government by taking the Tower of London and the Bank of England. Police learned of the plan and dispersed the meeting. Thistlewood attempted to flee to North America. He and three other leaders were arrested and charged with high treason. When James Watson was acquitted, the authorities released Thistlewood and the others as well.
When police arrested Thistlewood after the Spa Fields meeting, he had already bought tickets to travel to the United States. Thistlewood wrote to the Home Secretary Lord Sidmouth in 1817 to demand reimbursement. When Sidmouth failed to respond, Thistlewood challenged him to a duel and was imprisoned in Horsham Jail for 12 months.
Cato Street Conspiracy
On 22 February 1820 Thistlewood was one of a small group of Spenceans who decided, at the prompting of George Edwards, to assassinate several members of the British government at a dinner the next day. The group gathered in a loft in the Marylebone area of London, where police officers apprehended the conspirators. Edwards, a police spy, had fabricated the story of the dinner. Thistlewood was convicted of treason for his part in the Cato Street Conspiracy and, together with co-conspirators John Thomas Brunt, William Davidson, John Ings and Richard Tidd, was publicly hanged and decapitated outside Newgate Prison on 1 May 1820.
- Chase, Malcolm (2011). "Crime in Regency Thurrock". Panorama, The Journal of the Thurrock Local History Society (50).
- Execution of Thistlewood, Brunt, Ings, Tidd and Davidson. Retrieved 2011-06-24.