After a revolt and flood of ministerial resignations, Boris Johnson finally announced he would be stepping down as UK prime minister.
Speaking in Downing Street, he expressed regret at being forced out and revealed he would hang around until his successor was chosen.
So, who could be in the running to replace him?
It was Sunak’s resignation on Tuesday evening, alongside that of Sajid Javid, which kicked off the mass resignation of government ministers over the last few days.
Sunak, who served as Chancellor of the Exchequer – the UK’s finance minister – has long been considered a leading figure in the Conservative Party, and a likely next prime minister.
However, his standing took a knock earlier this year when it was revealed that his Indian wife had nom-domiciled tax status, meaning she didn’t pay UK tax on most of her income. Newspapers also reported that Sunak held a US green card while serving as Chancellor, which left some questioning his commitment to the country.
Having also been fined for attending a lockdown party in Downing Street, Sunak could also struggle to separate himself from some of the scandals of the Johnson era.
Even so, the 42-year-old remains one of the most prominent candidates to replace Johnson, though he will likely be challenged on his handling of the economy over the last few years and his plans for taxes and shrinking the state.
The son of a Pakistani immigrant bus driver, who became an investment banker and then politician, Javid has run for party leadership twice before: in 2016 and again in 2019. However, he may feel like now is his chance.
Javid previously resigned in early 2020, after clashing with Johnson over his team of advisers, but was brought back into the government to handle the coronavirus response.
Having held almost every senior cabinet position during his career – health secretary, chancellor, home secretary, business secretary, housing secretary and culture secretary – Javid will feel he is well-placed to lead the country.
Javid’s role in bringing to an end the Johnson era may aid his standing among some Tory grassroots, though it will certainly alienate others.
Britain’s current foreign secretary has been open about her leadership ambitions. Having been an MP since 2010, Truss has risen steadily up the ministerial ladder and is currently the longest continuously serving member of the cabinet.
Truss has held a wide range of cabinet roles, including environment and justice secretaries, and while she backed Remain in the 2016 referendum, she has since become a staunch defender of Brexit.
Truss is also one of the favourites on the leadership rankings put together by ConservativeHome, the party’s popular grassroots website. However, the concerns are that she may only appeal to a narrow section of the general population.
The current chair of the Foreign Affairs Select Committee, Tugendhat has already said he will run for Conservative party leadership.
Despite lacking ministerial experience, the former soldier is seen as a leading figure in the One Nation wing of the party and has been critical of Johnson throughout his premiership, in a way that has boosted his visibility and credentials.
Tugendhat has said that it would be a "huge privilege" to serve as prime minister.
Britain’s current home secretary, Patel has long been seen as the darling of the Conservative grassroots, with her strong stance on immigration and public spending.
Patel introduced a points-based immigration system and was the architect of the controversial deal to send asylum seekers to Rwanda. However, outside of the right wing of the party she might be seen as a difficult leader to take on the Labour Party in the next elections, which could dent her chances of becoming the next Tory party leader.
A November 2020 report by the prime minister's adviser on ministerial standards also found Patel had breached the ministerial code with behaviour that it said amounted to bullying.
Zahawi’s recent promotion to Chancellor of the Exchequer has given a boost to his profile and chance of becoming the next prime minister. However, his limited frontline political experience and public profile are likely to count against him.
The 55-year-old MP was appointed vaccines minister by Jonson during the coronavirus pandemic, then moved to education secretary. His appointment as Chancellor of the Exchequer when everyone else was jumping ship could be a positive or negative for Zahawi, and his letter to Johnson on Thursday morning telling him to resign has been seen by some as the final nail in the coffin for the outgoing prime minister.
Zahawi may be one of the first candidates to declare their intention to stand for prime minister after Johnson officially resigns, but he will have his work cut out to persuade fellow MPs to back him.
As deputy prime minister and justice secretary, Raab may take a caretaker role as prime minister if Johnson steps down before a new leader is chosen.
As Justice Secretary, Raab introduced a series of tough reforms in the legal and prison systems, but at the same time urged the public to forgive Johnson over his role in lockdown parties.
Raab previously served as foreign secretary, but finished sixth in the 2019 Conservative leadership election, meaning he may struggle to convince his colleagues that he has what it takes to lead the party forward.
Having been beaten by Boris Johnson in the last Conservative leadership election in 2019, Hunt may fancy another shot at running for party leadership.
The current chair of the Health and Social Care Select Committee, Hunt was previously foreign secretary and is seen as a grandee of the party.
Having been a backbencher throughout Johnson’s time in office, and critical of some of the government’s actions, he will also be able to effectively distance himself from the controversies of the last year or so.
Defence secretary Ben Wallace has won praise for his handling of the Ukraine crisis and his role in overseeing the evacuation of refugees and British nationals from Afghanistan.
While Wallace claims to have no interest in a leadership bid, his solid reputation and position as a long-term ally of Johnson could help him be seen as a compromise candidate.