Boris Johnson quit as Tory leader after admitting he failed to persuade Cabinet colleagues that he could fight on.
The Prime Minister said it was “eccentric” to change governments at this stage but “I regret not to have been successful in those arguments”.
A new Tory leader will now be elected who will replace Mr Johnson in No 10.
“In politics, no one is remotely indispensable,” he acknowledged in a statement delivered from a lectern in Downing Street.
“I want you to know how sad I am to be giving up the best job in the world, but them’s the breaks,” he said.
Protester Steve Bray could be heard in the background playing ‘Bye, bye Boris’ through speakers.
Watch the clip in full below: