Boris Johnson is the third Conservative prime minister to be brought down by Tory infighting in the space of six years.
A split over Europe ultimately led to David Cameron losing his Brexit gamble and resigning, while Theresa May failed to unite her warring MPs over plans to deliver on the outcome of the referendum. In Mr Johnson’s case, his own leadership caused a rift in the party.
Here we look at each prime minister’s downfall.
– David Cameron
Mr Cameron resigned on June 24 2016, bringing an abrupt end to his six-year premiership after the British public took the momentous decision to leave the European Union.
He pledged an in-out referendum in 2013 as a calculated gamble, aimed at silencing the Eurosceptics in his own party. Divisions over Europe were nothing new in the Conservative Party, but the issue was turbocharged by austerity and immigration, as well as the rise of Ukip.
Mr Cameron campaigned hard to remain, as Tory MPs bickered among themselves. He had to contend with the defection of many of his backbenchers and Mr Johnson, who became the figurehead of Vote Leave.
Ultimately Mr Cameron fell on his sword. Within hours of Remain’s defeat, he announced he would stand down, saying the nation needed “strong, determined” leadership for the exit negotiations ahead.
– Theresa May
Mrs May took over the party reins in July 2016, vowing to deliver Brexit.
And Brexit is what ended up entirely defining her almost three years in office and ultimately doomed her premiership, as her plans to deliver it failed again and again to satisfy her warring MPs.
She lost her party’s majority in the 2017 general election, and suffered humiliating defeats in Parliament when the withdrawal deal she agreed with the EU was rejected three times.
Conservative MPs angry at her Brexit policy launched a no-confidence vote against Mrs May in December 2018, which she survived.
But this failed to quell vocal opposition from within Tory ranks, with many ministers departing in protest.
She finally faced up to the demands from her MPs and resigned on May 24 2019.
– Boris Johnson
After spending months contributing to the destabilisation of Mrs May’s leadership, Mr Johnson arrived in Downing Street on July 24 2019.
Always a divisive figure, he was widely criticised for proroguing Parliament to get through a Brexit deal as one of his first acts as prime minister.
But he got many Tories back on his side when he won a large majority in the December 2019 election.
Conservative grievances with Mr Johnson’s leadership started seriously mounting last November when the Prime Minister attempted to overhaul the standards system in the Owen Paterson lobbying scandal.
A steady drip of partygate allegations soon followed, culminating in a police fine for Mr Johnson and Sue Gray’s damning report that blamed “failures of leadership and judgment” for allowing alcohol-fuelled gatherings in Downing Street when millions of people across the country were unable to see friends and family.
Mr Johnson was also accused of misleading Parliament over his knowledge of the lockdown-busting parties.
His authority was damaged by a confidence vote which saw 41% of his own MPs withdraw their support in June.
Defeat in two crunch by-elections later that month, triggered by the resignations of two Tory MPs in disgrace, and the subsequent surprise resignation of the Conservative Party co-chairman renewed calls for Mr Johnson to go.
But it was his handling of the Chris Pincher affair that saw Mr Johnson haemorrhage support across the Tory ranks.
