Home Secretary Theresa May is set to lead Britain from Wednesday evening when Prime Minister David Cameron hands over power after his post-Brexit resignation prompted the ruling Conservative Party to seek a successor.
Cameron will host a final prime minister's questions in parliament around midday before making a final speech to reporters around 1600 GMT and then visiting Queen Elizabeth II to inform her formally of his resignation.
May will then have her own audience with the queen before travelling back to 10 Downing Street, the prime minister's official residence in London, to speak to reporters.
In her acceptance speech on Monday, May said Britain needs a "vision of a country that works for every one of us," after last month's Brexit referendum exposed social, economic and political divisions.
"Brexit means Brexit and we are going to make a success of it," said May, who had backed Cameron's Remain campaign before the referendum. But she faces mounting pressure to begin talks on Brexit with European Union officials sooner than she had planned.
May had advocated waiting until the end of this year to invoke Article 50 of the Lisbon Treaty, which sets the rules for a nation leaving the EU, but many British and EU politicians have urged her to move more quickly.
Much attention will now focus on what roles, if any, May hands prominent Brexit campaigners Angela Leadsom, Boris Johnson, Michael Gove, Chris Grayling and Liam Fox in her new cabinet, amid speculation that one of those five could be given a new post of Brexit minister.
Cameron resigned after he failed to convince a majority of voters in a June 23 referendum on EU membership to oppose leaving the political bloc.