Boris Johnson, Andrea Leadsom, Michael Gove, Jeremy Hunt, Dominic Raab and Sajid Javid are the potential contenders
Another crushing Brexit defeat for Theresa May means the British prime minister is on the ropes again - now perhaps for the last time. Here is a list of potential contenders to take over as Conservative party leader and therefore prime minister:
A former mayor of London, "Boris" or "BoJo," was a key figure in the 2016 Brexit campaign but failed in his bid to become prime minister in the aftermath as ally Michael Gove withdrew his support at the last minute.
May appointed Johnson as foreign minister but he quickly drew attention for all the wrong reasons, including a series of diplomatic gaffes.
He became increasingly uncomfortable with the government's Brexit strategy before resigning in July.
Charismatic and popular with grassroots Conservatives, the 54-year-old has also earned plenty of enemies within the party for his behaviour.
He separated from his second wife in September and has a new girlfriend. He has recently lost weight and trimmed back his trademark mop of blond hair.
The 55-year-old came second to May in the 2016 contest to replace David Cameron. She is the leader of the House of Commons - responsible for bringing government business before the chamber - and is a staunch Brexiteer.
She has earned plaudits from the right-wing of the party for standing up to House of Commons speaker John Bercow, seen by critics as partial on the issue of Brexit.
Leadsom has also pushed for an end to the culture of sexual harassment and bullying in parliament.
She started out in the financial sector and later became an energy minister under Cameron but was little known before the Brexit vote.
She pulled out of the leadership content after appearing to suggest that May was less well placed to become leader because she was not a mother.
Brexit campaigner Gove initially supported Johnson's leadership bid in 2016 but at the last minute announced his own intention to run, causing both men to lose out to May.
"Whatever charisma is, I don't have it," he admitted in the race in which he came third.
After a year in the political wilderness, he was appointed environment minister in June 2017 and has stayed in the headlines with a series of eco-friendly policy announcements.
Equally active in his previous justice and education briefs, he is a minister who likes to see through radical new policies.
Following a series of resignations, the cerebral 51-year-old is now undeniably the leading eurosceptic in government.
The foreign minister supported remaining in the EU but has been highly critical of what he calls the "arrogant" approach taken by Brussels.
A former businessman who speaks fluent Japanese, the 52-year-old is a resilient politician, having headed up the National Health Service for six years during a funding crisis.
He replaced Johnson as Britain's chief diplomat. Softly spoken and measured, Hunt is calm under fire and has gradually seen his power and influence in cabinet rise.
An ardent eurosceptic with a black belt in karate, the 45-year-old has quickly climbed the ministerial ladder.
Raab only joined the government in 2015 under Cameron.
He backed Brexit and was named justice minister in the new cabinet after the 2016 referendum.
Raab later served as Brexit secretary from July to November 2018 when he stepped down in protest at the Brexit deal struck with the EU.
Just before his departure, he was widely mocked for saying that he "hadn't quite understood" how reliant UK trade in goods is on the Dover-Calais crossing.
A former investment banker and the son of a Pakistani immigrant bus driver, the 49-year-old Javid is the face of a modern, multicultural and meritocratic Britain.
On the economically liberal wing of the Conservative Party, Javid voted for Britain to stay in the EU in 2016.
Since being appointed interior minister in April 2018, he has earned respect for his handling of a scandal over the treatment of the children of Caribbean immigrants, known as the Windrush generation.
However, he was recently criticised in liberal circles for stripping a teenage mother who ran away to join the Islamic State group of her British nationality.