Theresa May will officially step down as the leader of the Conservative Party on today, but will remain as prime minister until her successor is chosen.
She announced her resignation two weeks ago, saying it was a matter of deep regret that she had been unable to deliver Brexit.
Eleven Conservative MPs are vying to replace her as party leader and, ultimately, prime minister.
The winner of the contest is expected to be announced in the week of 22 July.
Mrs May remains acting party leader during the leadership election process.