Britain's shock decision to quit the EU could be the defining moment in the political career of ex-London mayor Boris Johnson.
The Uxbridge MP is likely to be the front runner to replace David Cameron if the Prime Minister resigns.
Johnson's decision in February to join the Leave campaign was a huge blow to Mr Cameron.
The former Mayor quickly emerged as the campaign's figurehead as he and the Prime Minister were pitched into battle on opposite sides.
Johnson's father Stanley said the referendum result meant his son was entitled to take part in a Tory leadership contest.