Boris Johnson will become prime minister on Wednesday after securing victory in the battle for the Conservative Party leadership.

The former foreign secretary, who was the firm favourite to win the contest, defeated Jeremy Hunt in the ballot of Tory members.

He will be appointed as prime minister on Wednesday by the Queen after Theresa May formally resigns from the office.

Mr Johnson secured 92,153 of the vote compared to 46,656 for Mr Hunt to win the Tory leadership.

Mrs May will take one last round of Prime Minister’s Question in the Commons on Wednesday before travelling to Buckingham Palace to offer her resignation.

Mr Johnson will then have his own audience with the Queen to be offered the chance to form her new government before entering Downing Street.

He faces a daunting in-tray at Number 10, including keeping his “do or die” promise to meet the looming Brexit deadline of October 31.

Mr Johnson will also have to navigate the diplomatic crisis in the Gulf, where tensions have been heightened following Iran’s seizure of the British-registered Stena Impero tanker.

The challenge facing Mr Johnson is made even more difficult by a wafer-thin Tory-DUP majority of two in the Commons, with the prospect of it being reduced to just one if the Conservatives fail to win the Brecon and Radnorshire by-election on August 1.

The incoming premier has been left in no doubt about the opposition he will face from his own benches if he attempts to force through a no-deal Brexit.

Sir Alan Duncan quit as a Foreign Office minister on Monday and Anne Milton as Education minister on Tuesday, rather than serve under Mr Johnson.

Cabinet ministers Philip Hammond, David Gauke and Rory Stewart are expected to join them on the backbenches after the leadership change.

Justice Secretary Mr Gauke said he believed there were “parliamentary mechanisms” which could prevent a no-deal Brexit that would “not necessarily” involve bringing down a Johnson administration.

He told BBC Radio 4’s Today that there was a “clear majority” in the House of Commons against a no-deal Brexit, and warned there were circumstances which could result in Mr Johnson losing a confidence motion – although Mr Gauke stressed he would not vote to bring down a Tory government.

“Are there circumstances where there is a risk of a government losing a confidence motion? Yes, clearly there are circumstances where there is a risk that that might happen,” he said.

“I think that the new prime minister would be wise to avoid getting into those circumstances.”

Former defence secretary Sir Michael Fallon, a supporter of Mr Johnson, said a combination of the incoming prime minister’s optimism and “plenty of goodwill” in the Brexit talks could achieve a deal.

“Let sunshine win the day,” Sir Michael told Today. “Boris is optimistic about this, he is ambitious about this.

“We have three months to get wording that Parliament will approve.”

David Hughes is PA Political Editor.