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Before the Union of England and Scotland in 1707, the figure of the prime minister can be compared to that of the Lord High Treasurer^[12] who led the Treasury of England. By the late Tudor period, the Lord High Treasurer was regarded as one of the Great Officers of State,^[12] and was often (though not always) the dominant figure in government: Edward Seymour, 1st Duke of Somerset (lord high treasurer, 1547–1549),^[13] served as lord protector to his young nephew King Edward VI;^[13] William Cecil, 1st Baron Burghley (lord high treasurer, 1572–1598),^[14] was the dominant minister to Queen Elizabeth I;^[14] Burghley's son Robert Cecil, 1st Earl of Salisbury, succeeded his father as Chief Minister to Elizabeth (1598–1603) and was eventually appointed by King James I as lord high treasurer (1608–1612).^[15]

By the late Stuart period, the Treasury was often run not by a single individual (i.e., the lord high treasurer) but by a commission of lords of the Treasury,^[16] led by the first lord of the Treasury. The last lords high treasurer, Sidney Godolphin, 1st Earl of Godolphin (1702–1710) and Robert Harley, 1st Earl of Oxford (1711–1714),^[17] in fact ran the government of Queen Anne^[18] and therefore can be considered de facto prime ministers.^[19]

Following the succession of George I in 1714, the arrangement of a commission of lords of the Treasury (as opposed to a single lord high treasurer) became permanent.^[1] For the next three years, the government was headed by Charles Townshend, 2nd Viscount Townshend, who was appointed Secretary of State for the Northern Department.^[2] Subsequently, Lords Stanhope and Sunderland ran the government jointly,^[3] with Stanhope managing foreign affairs and Sunderland domestic.^[3] Stanhope died in February 1721 and Sunderland resigned two months later;^[3] Townshend and Robert Walpole were then invited to form the next government.^[4] From that point, the holder of the office of first lord also usually (albeit unofficially) held the status of prime minister. It was not until the Edwardian era that the title prime minister was constitutionally recognised.^[5] The prime minister still holds the office of first lord by constitutional convention,^[6] the only exceptions being Lords Chatham (1766–1768) and Salisbury (1885–1886, 1886–1892, 1895–1902).^[7]

Due to the gradual evolution of the post of prime minister, the title is applied to early prime ministers only retrospectively;^[5] this has sometimes given rise to academic dispute. William Pulteney, 1st Earl of Bath and James Waldegrave, 2nd Earl Waldegrave are sometimes listed as prime ministers.^[81] Bath was invited to form a ministry by George II when Henry Pelham resigned in 1746,^[82] as was Waldegrave in 1757 after the dismissal of William Pitt the Elder,^[83] who dominated the affairs of government during the Seven Years' War. Neither was able to command sufficient parliamentary support to form a government; Bath stepped down after two days^[81] and Waldegrave after four.^[83] Modern academic consensus does not consider either man to have held office as prime minister;^{[84][failed verification]} they are therefore listed separately.

• "Past Prime Ministers". Gov.uk. UK Government. Archived from the original on 25 August 2008.
• "Prime Ministers and Politics Timeline". History. BBC. Archived from the original on 27 May 2011.