Langston was the oldest son of James Langston and his wife Sarah, of Sarsden House in Oxfordshire. In 1784 he married Sarah Goddard, daughter of John Goddard of Woodford Hall, Essex. They had one son and four daughters.
Langston was a director of the Sun Fire Office from 1794 until his death. He aimed to buy himself a place in Parliament, but never found a safe seat. At the 1784 election he was returned after a contest as a Member of Parliament for Sudbury, an open borough with a reputation for venality where the government backed his candidacy. At the next election, in 1790, he contested Bridgwater in the interest of the 4th Earl Poulett. The Earl of Egmont had funded his son Viscount Perceval to contest the seat, but Langston and Poulett's brother Vere won by a comfortable margin. Having joined the opposition, Langston was no longer acceptable to Poulett, so he turned instead to Minehead, where opposition was mounting to the "overbearing conduct" of the borough's patron John Fownes Luttrell, whose Dunster Castle-based family had dominated the borough for most of the period since its 16th-century enfranchisement. Langston bought some building land in Alcombe, within the borough, from a Quaker William Davis who had advertised for a wealthy challenger. There he rapidly built some houses to register voters, and nominated himself and his wife's brother-in-law Admiral Charles Morice Pole. At the election in 1796John Fownes Lutrell held his own seat, but Langston defeated his brother Thomas Fownes Luttrell. Luttrell rallied his support by the next election in 1802, and defeated Langston, whose illegal treating of voters after the arrival of the writ, had not been enough to win. An election petition was prepared, but after a period of negotiations, Langston sold all his Minehead interests to Fownes Luttrell. Out of Parliament, Langston was Sheriff of Oxfordshire in 1804–05. He was returned to the Commons in March 1806 for the Irish rotten borough of Portarlington, whose patron the 2ndEarl of Portarlington accommodated Langston as a favour to the Prince of Wales. At the general election in 1806, Langston returned to Bridgwater, where he won a contested election with Vere Poulett again returned as his running-mate. However, by 1807 the earl had disowned his brother's politics, and Langston withdrew. Langston never returned to Parliament, and died in 1811, aged about 54.
