This is a list of prime ministers of the United Kingdom by length of tenure. This is based on the difference between dates; if counted by the number of calendar days, the figures would be one day greater for each term served.
The term prime minister appeared in the early eighteenth century as an unofficial title for the leader of the government, usually the head of the Treasury.[1] Jonathan Swift, for example, wrote that in 1713 there had been "those who are now commonly called Prime Minister among us", referring to Sidney Godolphin and Robert Harley, Queen Anne's lord treasurers and chief ministers.[2] Robert Walpole is regarded as the first prime minister; he became First Lord of the Treasury of Great Britain in 1721. This list includes all prime ministers of the Kingdom of Great Britain, the United Kingdom of Great Britain and Ireland, and the modern-day United Kingdom of Great Britain and Northern Ireland.