When does Andy Burnham become prime minister and what are his policies?
Sir Keir won a landslide general election victory two years ago but began to lose public support after a series of policy missteps and U-turns.
The final straw for most Labor MPs was when the right-wing Reform UK party made huge gains in local elections in May, causing many to fear that Reform leader Nigel Farage would win the next general election.
Burnham has long had ambitions of becoming Labor leader, but has only been able to challenge for the top job as an incumbent MP.
He returned to Parliament in a by-election a month ago and his victory over the Reform candidate convinced many Labor MPs that he was the right person to replace Sir Keir.
Other senior figures in the Labor Party, such as former health minister Wes Streeting, abandoned their own leadership bids and threw themselves behind Burnham, along with an overwhelming majority of party MPs.
This meant he became leader of the Labor Party without any contest.
In the UK, prime ministers are not directly elected. For example, unlike the presidents of the United States or France, they are the leaders of the party with the most MPs in the House of Commons.
This means the UK can change its prime ministers without an election; This is something that has been happening with increasing frequency in recent years.
