List of Prime Ministers of the United Kingdom

The Prime Minister of the United Kingdom is the head of Government of the United Kingdom and chairs Cabinet meetings. There is no specific date when the office of Prime Minister first appeared, as the role was not created but evolved over a period of time. The term was used in the House of Commons in 1805, it was certainly in Parliamentary use by the 1880s, and in 1905 the post of Prime Minister was officially given recognition in the order of precedence. Modern historians generally consider Sir Robert Walpole, who led the government of Great Britain for 21 years in 1721–42, as the first Prime Minister to serve; Walpole is also the longest-serving British prime minister. However, Sir Henry Campbell-Bannerman was the first titular Prime Minister and Margaret Thatcher the longest-serving Prime Minister to be officially referred to as such.

Strictly, the first "prime minister" of the United Kingdom (of Great Britain and Ireland) was William Pitt the Younger. The first Prime Minister of the current British state, the United Kingdom of Great Britain and Northern Ireland, was David Lloyd George, although the country had not been renamed officially until 1925 when Stanley Baldwin was Prime Minister.

Due to the gradual evolution of the post of Prime Minister, the title is applied to early Prime Ministers only retrospectively; this has sometimes given rise to academic dispute. William Pulteney, 1st Earl of Bath and James Waldegrave, 2nd Earl Waldegrave are both sometimes listed as Prime Ministers. Bath was invited to form a ministry following the resignation of Henry Pelham in 1746, as was Waldegrave in 1757 following the dismissal of William Pitt the Elder (the predominant minister of the first Devonshire ministry). Neither was able to command sufficient Parliamentary support to form a government; Bath stepped down after two days, and Waldegrave after four. Modern academic consensus does not consider either man to have held office as Prime Minister, and they are not listed.

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