David Cameron has announced he will stand down as Prime Minister by October.
Here we look at some of the potential contenders to replace him:
The former London mayor is one of the frontrunners to succeed his Old Etonian school chum at No 10. Johnson previously insisted he had less chance of taking the top job than being "reincarnated as an olive" but his protestations have done little to disguise his ambitions.
At the weekend he summoned friendly Tory MPs to his Oxfordshire home in likely preparation for a run. After leading the Brexiteers to victory, his stock among Conservative grassroots Eurosceptics will be higher than ever. But Tory leadership contests have a funny habit of failing to return the dead cert. Ex-minister Alan Duncan said despite Johnson's "excitement and notoriety", many activists did not want a "permanent ride on the big dipper".
Hanging on to the Home Secretary brief, which notoriously ruins political careers, for six years shows May's durability. Although a Remain supporter, she disappeared off the radar during the campaign, leaving her relatively unscathed.
No fan of Cameron, she has been quietly courting the party's rank and file in readiness for his departure and has been tipped as the most popular candidate among Conservative voters in a YouGov poll. Some MPs - including Iain Duncan Smith - have publicly urged MPs not to consider candidates who did not support Brexit in the referendum campaign. International Development Secretary Justine Greening has appealed to May and Johnson to form a "united leadership" to help bring the country back together.
The Health Secretary recently said his current brief would be his "last big job in politics" but has now revealed he is "seriously considering" a bid for the Conservative leadership. A Remain supporter, he has called for the public to be given a say on Britain's terms for leaving the European Union. He faced a bumpy ride over his handling of News Corporation's takeover bid for BSkyB when culture secretary but managed to see out the turbulence.
The Justice Secretary has seen his public profile increase over the last few weeks and, bar the occasional sticky moment, he is generally regarded to have had a good campaign. The bookies' odds on Gove, whose once-close friendship with Cameron has come under strain as the rough and tumble of the battle took its toll, becoming leader have tumbled.
But many believe he is more likely to seek an influential role in a Johnson-led administration, possibly as deputy prime minister leading the negotiations over the UK's exit from the EU.
The Work and Pensions Secretary is hugely popular in the Conservative parliamentary party and comes from the sort of ordinary background that chimes with many voters. The former Welsh secretary says the party should be led by someone "who understands the enormity of the situation we're in and who has got a clear plan to deliver on the expectations of the 17 million people who voted to come out last week", including keeping the United Kingdom together. But the sudden contest may come a little too soon for him to make much headway even as a unity candidate.
The son of a Pakistani bus driver who went on to become a managing director at Deutsche Bank, the Business Secretary - the first Asian male in a Tory cabinet - has long been talked of as a future leader. His chances may be hampered however by claims by former colleagues that he backed Remain while privately supporting Brexit.
His handling of the Tata Steel crisis also drew criticism. He says the "party has lots of talents" on both sides of the argument and he is "not going to guess" who will be in the running. There have been reports that Javid could stand on a joint ticket as potential chancellor with Crabb.
The Education Secretary has not ruled out a run, saying that she wanted there to be a woman in the final two candidates between whom party members get to choose. "If that is me or someone else it is too early to tell. I would think about it but it is about what other colleagues are looking for in the next leader." She would represent a moderate continuation of the Cameron legacy. Her support for Remain may count against her.
The Scottish Conservative leader has impressed many with her performance during the campaign and electoral success north of the border last month. But a Westminster seat would need to be found for her to have a viable shot at the top job. Ms Davidson has also suggested such a move is not for her, describing life at No 10 as lonely.
The former defence secretary - who unsuccessfully sought the top job in 2005 - was the first to confirm he was considering a fresh bid. An outspoken supporter of Brexit, he would hope to win over the right of the party.
An assured performance by the energy minister for the Brexit side in the referendum campaign has sparked talk of the former banker and fund manager seeking a rapid promotion to the top job. She has declined to rule out a tilt, revealing she was "looking at all sorts of angles and considering".
Another to have dramatically increased their public profile through a prominent place in the successful push to get Britain out of the EU, the employment minister is also tipped as a potential contender. On the right of the party, she is a supporter of the restoration of capital punishment for the most serious crimes.