Tory leadership hopefuls Boris Johnson and Jeremy Hunt have both said it's "all to play for" as Britain waits to learn who will become the next prime minister.

Foreign Secretary Mr Hunt was in a positive mood when he arrived home from a run on Tuesday morning despite Mr Johnson remaining the clear favourite to take over from Theresa May.

With the result expected around midday today, Mr Hunt said it was still "all to play for", a comment echoed by his rival as he entered his campaign headquarters.

A Johnson win could spark more Government resignations after Sir Alan Duncan quit as Foreign Office minister on Monday in protest at his expected victory, predicting a "crisis of government" if Mr Johnson becomes PM.

Ministers opposed to his "do or die" pledge to pull the UK out of the EU on October 31, even if there is no deal in place, could leave before Mrs May formally gives up the premiership on Wednesday afternoon.

Chancellor Philip Hammond and Justice Secretary David Gauke have given notice that they will resign rather than serve under Mr Johnson.

Mrs May will tender her resignation to the Queen after taking Prime Minister's Questions in the Commons on Wednesday afternoon for the final time, with the new Tory leader set to enter Number 10 soon afterwards.

The new prime minister will have to govern with a Tory-DUP majority of just two, after Dover MP Charlie Elphicke had the Conservative whip suspended when he was charged with sexually assaulting two women.

The Government majority could be further reduced next week if the Tories lose the Brecon and Radnorshire by-election.