Waiting in the wings? Tory runners and riders
Theresa May has survived the week but her leadership remains under threat following the resignations of Boris Johnson and David Davis. As Eurosceptic Tory MPs weigh up their next move, Steven Swinford assesses who is in pole position.
Boris Johnson's spectacular resignation has already led to fevered speculation about a future leadership bid. He has been repeatedly written off by his critics but remains hugely popular with Eurosceptic Tory MPs, having championed their cause relentlessly in Cabinet - often in the face of caustic opprobrium from his colleagues.
The EU referendum polarised public opinion about Johnson, but his shock resignation will only increase his high profile and his hard line on Brexit could win him significant support.
The key question for Johnson is whether he will be able to muster enough support from fellow Tory MPs to make it to the final two of the Tory leadership contest. If he can make it through to the vote of Tory activists, few would bet against him.
The Home Secretary has won plaudits with both Remainers and Brexiteers for repeatedly taking on the Prime Minister - and winning. He joined forces with Greg Clark and Jeremy Hunt to secure a significant climbdown from the Prime Minister on visas for highly-skilled migrants.
He also publicly questioned the Prime Minister's net migration target and was heavily critical of the hostile environment policy for illegal immigrants in the wake of the Windrush scandal.
Tory Eurosceptics once said they could never forgive him after he decided at the last minute to back Remain after flirting with Brexit.
However, since his appointment as Home Secretary they have been delighted with the way he has embraced Brexit, in particular his decision to side with Boris Johnson and David Davis in rejecting Theresa May's customs partnership.
The Environment Secretary has played his cards very carefully in recent weeks.
While privately he has raised significant concerns about Theresa May's Brexit policy and even ripped up a page of her customs partnership plan during one meeting, publicly he has been far more reticent.
His interview with Andrew Marr on the BBC last weekend was a case in point, backing the Prime Minister's plan as a "proper" exit from the European Union. While he said the Chequers compromise was not what he had hoped for, he added that he was a "realist". His comments are in stark contrast to those of Boris Johnson, who described the Brexit plan at Chequers as a "turd".
There remains a significant level of mistrust between the two men after Gove stabbed Johnson in the "back, front and side" during the last Tory leadership contest, and many Eurosceptics still view him with suspicion.
However, he has been actively courting fellow MPs and speaking at innumerable think-tank events. As Environment Secretary, his war on single-use plastic is one of the few genuinely popular domestic policies and May has put it at the heart of her agenda. Could his political renaissance take him all the way to the very top?
The former health secretary has been given Boris's old job by May, but could he be a dark horse in the race for the Conservative Party leadership?
Hunt has established himself as a firm Eurosceptic despite having backed Remain during the EU referendum.
He recently criticised Airbus after it threatened to pull investment from Britain, describing its intervention as "completely inappropriate" and urging the country to ignore "siren voices".
He is seen by some as a compromise candidate, and is said to have taken to inviting colleagues in groups of eight or 10 for meetings with sandwiches in Portcullis House. As health secretary he won a significant battle to secure £20bn a year in extra funding for the NHS, although he could face a backlash from Tory colleagues if it is funded by tax rises.
The Defence Secretary has been locked in an extraordinary row with the Prime Minister over defence funding, and has been accused of telling officials that he could bring her down. "I made her and I can break her", he is alleged to have said - although aides deny he used that form of words.
The former Chief Whip is said to visit the tearooms every morning, where he has been seen meeting Eurosceptics MPs.
Like Jeremy Hunt, Williamson has become a keen Brexiteer himself, having joined Javid in arguing against the customs partnership.
However, his elevation to the role of Defence Secretary has alienated some of his colleagues, who also have concerns about his confrontational style.
Among Tory Eurosceptics, Rees-Mogg is a man who can do no wrong. As leader of the European Research Group of Eurosceptic Tory MPs, he has taken a distinctly tougher approach than his predecessor and been merciless in his criticism of Theresa May over Brexit.
He has to date stopped short of directly calling for the Prime Minister's head, although he has come remarkably close. He recently compared May to Sir Robert Peel, the former Tory Prime Minister forced to resign after a mass revolt by his party over the Corn Laws.
Rees-Mogg has always eschewed any leadership ambitions and insisted that his focus is on keeping May to her promises on Brexit.
And as much as he is loved by Eurosceptics, he was recently branded "insolent" by one Tory minister. At the very least Rees-Mogg is likely to be a king-maker, but there are some who believe he could end up going all the way.
Odds valid at time of going to press