Who is the longest serving Prime Minister? PMs with longest time in office as Liz Truss resigns

Liz Truss is expected to leave Downing Street by the end of next week after announcing her resignation as the leader of the Tory party, and as Prime Minister. It comes after a chaotic 44 days in office, with Truss cementing herself in the history books as the shortest serving Prime Minister in history.

A little over 24 hours after insisting she was “a fighter, not a quitter”, she stood at a lectern in Downing Street and said she had informed the King she was resigning as Tory leader. The Tories will now scramble to find a replacement who will become the third leader in two months amid calls for a general election.

But with all eyes on Truss as the Prime Minister with the shortest time in office, who in history had the longest tenure?

This is everything you need to know.

Who is the longest serving Prime Minister?

The Prime Minister with the longest tenure was that of Sir Robert Walpole,  traditionally considered to be the first Prime Minister, whose single term in office lasted 20 years and 315 days, starting on 3 April 1721 and ending on 11 February 1742. His one term outlasts the accumulated terms of every other Prime Minister.

Walpole was a member of the Whig party which, in the 1850s, merged into the Liberal Party. In 1866, a number of Whigs left the party in order to form the Liberal Unionist Party, which then merged into the Liberals’ rival in 1912, the modern day Conservative Party.

Others who spent the longest time as Prime Minister also include:

• William Pitt the Younger, who spent two terms in office, with a tenure length of 18 years and 343 days, from 1783 to 1801, and then again from 1804 to 1806
• The Earl of Liverpool, Robert Banks Jenkinson, spent 14 years and 305 days as Prime Minister across a single term, from 1812 to 1827
• The Marquess of Salisbury, Robert Gascoyne-Cecil, whose tenure of 13 years and 252 days was spread across three terms, from 1885 to 1886, 1886 to 1892 and 1895 to 1902
• William Ewart Gladstone, who spent 12 years and 126 days in office across four terms, from 1880 to 1885, 1868 to 1874, 1886 to 1886 and 1982 to 1894
• Lord North, Frederick North, who spent 12 years and 58 days in office during his single term, from 1770 to 1782 

Who is the shortest serving Prime Minister?

Liz Truss has entered into the history books as the shortest serving Prime Minister to have ever taken office. In contrast to the longest serving PMs, who spent, at minimum, 12 years total in office, Truss lasted a whopping 44 days, not including the day of her resignation.

George Canning previously held the record of shortest serving Prime Minister, whose singular term lasted less than a year - 199 days in total. He took office on 12 April 1827 and served until his death later that year, on 8 August 1827.

It could be argued that William Pulteney (Lord Bath) and James Waldegrave (2nd Earl Waldegrave) enjoyed even shorter periods than Truss and Canning, with two and four days respectively - however, neither actually formed an effective government.

Arthur Wellesley (1st Duke of Wellington) also formed a caretaker administration that lasted 25 days.

But if we’re looking specifically at those with clear terms, then Truss takes the title by a mile.