Boris Johnson has ruled himself out of the Tory party leadership contest to replace Prime Minister David Cameron.
In a dramatic press conference just moments before the deadline for nominations passed, Mr Johnson said that the next Tory leader would have to unify his party and ensure that Britain stood tall in the world.
The former Mayor of London and MP said: "Having consulted colleagues and in view of the circumstances in Parliament, I have concluded that person can not be me.
"My role will be to give every possible support to the next Conservative administration to make sure we properly fulfil the mandate of the people that was delivered at the referendum and to champion the agenda I believe in."
It came after the shock announcement by fellow Brexit campaigner Michael Gove - who had widely been expected to be Mr Johnson's running mate - that he was putting himself forward for the leadership.
Johnson's decision not to join the battle leaves Home Secretary Theresa May as hot favourite to be the next Prime Minister.
He made supporters and journalists wait until the end of his speech before revealing his intentions, just moments before the official announcement from the Tories 1922 Committee that there would be five candidates in the contest - Mr Gove, Mrs May, Work and Pensions Secretary Stephen Crabb, former defence secretary Liam Fox and pro-Brexit energy minister Andrea Leadsom.
Britain had a chance "to think globally again, to lift our eyes to the horizon, to bring our uniquely British voice and values, powerful, humane, progressive, to the great global forums without being elbowed aside by a supranational body" and the agenda for the next PM would be to "seize this chance and make this our moment to stand tall in the world", said Mr Johnson.
But he added: "I must tell you, my friends, you who have waited faithfully for the punchline of this speech, that having consulted colleagues, and in view of the circumstances in Parliament, I have concluded that person cannot be me.
Aides at Boris event covered up the emergency exit sign to foil the inevitable photo pic.twitter.com/33RoIHpBzZ— Katherine Haddon (@khaddon) June 30, 2016
"My role will be to give every possible support to the next Conservative administration, make sure we properly fulfil the mandate of the people that was delivered at the referendum and to champion the agenda I believe in."
Meanwhile, Mrs May launched her bid for Number 10 with a message that the country needed "strong leadership" at a time of economic and political uncertainty and - in a clear swipe at Mr Johnson - warned that politics was not a "game". Contrasting herself with those who enter politics out of "ideological fervour" or "ambition or glory", she said she was a "public service" politician who was not "showy" but could "get the job done".
"If you are from an ordinary working class family, life is just much harder than many people in politics realise," she said.
"Frankly, not everybody in Westminster understands what it's like to live like this and some need to be told that it isn't a game. It's a serious business that has real consequences for people's lives."
Mrs May - who was a low-key supporter of Remain during the referendum - made clear she will not attempt to back away from last week's vote to leave the EU, saying: "Brexit means Brexit."
In a further olive branch to Leave supporters, she said she would create a new Government department, headed by a Cabinet-level minister who had campaigned for Leave, to oversee the UK's departure from the EU.