Thomas Slingsby Duncombe (1796 – 13 November 1861) was a Radical politician, who was a member of the Parliament of the United Kingdom for Hertford from 1826 to 1832 and for Finsbury from 1834 until his death. Duncombe was a tireless champion of radical causes in the 27 years he served the North East London borough of Finsbury. But he was equally well known for his style; he was, it was often said, "the handsomest and best-dressed man in the house," and his love for theatre, gaming and women were well publicized. Duncombe was elected and then returned to his seat seven times by the shopkeepers, artisans and laborers, the Nonconformists, Catholics, and Jews of Finsbury, making him the longest-sitting representative of a metropolitan borough in his day. His constituents called him "Honest Tom Duncombe" with great affection; to his detractors he was known as the "Dandy Demagogue" or the "Radical Dandy." His name was celebrated in working men’s newspapers and frequently mentioned in the gossip sheets of high society. Duncombe was, as The Times put it delicately upon his death, a "character."
Duncombe was born wealthy and well-connected in 1796 in Middlesex. His parents, Thomas and Emma Duncombe, had an estate in the West Riding of Yorkshire. He was the grandson (on his mother's side) to the Bishop of Peterborough, and nephew to the first Baron Feversham. He attended Harrow school from 1808 to 1811, leaving to take up a commission in the elite regiment of the Coldstream Guards. While in the Guards, Duncombe served as aide-de-camp to General Sir Ronald Ferguson. As Ferguson was well known for supporting the ballot and other political reforms during his time in Parliament, it is likely that it was here that Duncombe had his first political awakening as a radical. After being raised to the rank of Lieutenant, Duncombe resigned from the army in 1819.