Andrea Leadsom, a candidate to become the next Conservative Party leader and British prime minister, rules herself out of the leadership battle during a news conference in central London, Britain July 11, 2016.
Senior Brexiteer Chris Grayling will be rewarded for his role running Mrs May's campaign, possibly replacing her as Home Secretary, and it is thought that a prominent Leave campaigner could be given the job of overseeing negotiations for the UK's departure form the European Union and make good on the new PM's promise that "Brexit means Brexit".
The politician is the latest to fall in an extraordinary two-and-ahalf weeks.
Cameron will now meet with his cabinet, including chancellor George Osborne and foreign secretary Phillip Hammond, and is expected to be paid tribute by his colleagues, led by the home secretary May. On Wednesday I will attend the House of Commons for Prime Minister's Questions. The next scheduled general election is in 2020, five years after the Conservative Party won its parliamentary majority in 2015.
May was officially named Conservative Party leader and successor to Cameron "with immediate effect" Monday, said Graham Brady, chair of the 1922 Committee, a collection of Conservative members of Parliament key to electing the party leader.
May was left as the only contender standing after the withdrawal from the leadership race of Andrea Leadsom, who faced criticism for suggesting she was more qualified to be premier because she had children.
Mrs Leadsom ruined her chances of gaining more support from Tory MPs when she was reported in a newspaper interview at the weekend as saying she was more suited to the leadership because she is a mother.
In a day of fast moving events, David Cameron - who will be remembered as the prime minister who triggered Britain's departure from the European Union - said he would hand over to Theresa May on Wednesday and gave his backing to his successor.
Cameron's resignation announcement the day after the June 23 referendum triggered the Tory leadership race.
Her surprise announcement stunned her supporters who believed she would have been a potential victor among numerous 150,000 party members set to decide which of the two to choose. The contest had been due to be decided by the party's grassroots members before Leadsom pulled out.
Despite Cameron's resignation, the 45-year-old remains a powerful figure in the Conservative party and could get a role in May's Brexit cabinet. She has a reputation for solid, unflashy competence and for prevailing over her rivals. May, 59, would become the second woman to lead Britain, after Margaret Thatcher, who governed from 1979 to 1990.