The 1922 Committee, which is made up of all Conservative backbench MPs, can expect to hear from Boris Johnson later.

Today Programme
BBC Radio 4

Image source, Reuters

"I hope he'll win, and I hope he'll win well," says former defence secretary Michael Fallon, in support of Boris Johnson.

He says that the public "expect us to get on and implement" Brexit three years on from the original referendum. He adds that he expects the EU will want to renegotiate the exit deal.

Focusing on leaving at the end of October "concentrates minds in Parliament" he says, adding that EU partners will want to help the UK leave.

He says he doesn't agree that the government will face problems from "day one".

"The party today will come together" and will "cheer on the winner", he tells the programme.

"Our partners in Europe have no interest in no deal, it will damage them and it will damage us," he states.

Image source, PA

Boris Johnson entered his campaign headquarters in Westminster just after 08:00 BST.

Asked if he agreed with Mr Hunt it was still all to play for, Mr Johnson said: "All to play for."

Boris Johnson is trending on Twitter with over 90,000 tweets mentioning his name ahead of the Conservative leadership announcement later.

With Mr Johnson the favourite to be named the next prime minister, the hashtag #BorisDay has emerged, while #primeminister has over 200,000 mentions.

Where do the potential new prime ministers stand on key issues?

Here's a quick guide to their positions on Brexit, immigration, tax, spending, health and social care and education.

Today Programme
BBC Radio 4

Image source, PA Media

Justice Secretary David Gauke tells the BBC's Today programme that he could not back a no confidence vote against a Tory government.

And despite making it clear that he will not serve under Mr Johnson's government, he said he wanted him "to succeed" in delivering a Brexit deal.

"I want Boris Johnson, if he wins today, to succeed.

"I think he needs to be given an opportunity to go out there, to engage the European Commission, with European member states, and make progress reaching the deal he clearly wants to reach."

BBC Breakfast

New Liberal Democrat leader Jo Swinson says she’s not planning on working with Boris Johnson or Jeremy Hunt because she "fundamentally" disagrees with them over Brexit.

“Both of those people are Brexiteers, they’re advocating a course of action that will be catastrophic for our country," she tells BBC Breakfast.

Ms Swinson, who was named the next Lib Dem leader on Monday, says she will continue to work with MPs from all different parties on the People's Vote campaign, which wants another EU referendum.

She adds: "I think that working together is important to secure the right future for our country.

"On Brexit I have a fundamental disagreement with Boris Johnson, Jeremy Hunt, and for that matter Jeremy Corbyn."

Who is new leader Jo Swinson?

Residents of the UK's most Brexit-supporting town share their thoughts on Scottish independence.

Read more here.

BBC Breakfast

BBC Brussels reporter Adam Fleming says if Boris Johnson becomes the next prime minister, he expects EU leaders to take a “friendly” but “firm” approach when dealing with him.

“Friendly, because they think if anyone can sell the Brexit deal to the British Parliament it would be Boris Johnson," he says.

"Firm, because they are opposed to lots of the ideas he has been putting forward.”

He adds that the EU is eager to know who the new PM’s team will be as that is who they will be negotiating with on a day-to day basis, and they are also desperate to know when the new PM will start making decisions about Brexit.

Today Programme
BBC Radio 4

Big political figures in the Tory party, like Philip Hammond and David Gauke, might be prepared to join the "growing band of Tory MPs who now seem to be mustering on the backbenches" to oppose a no-deal Brexit, says BBC assistant political editor Norman Smith.

"They take the view they don’t have to hold back in any way at all because these are politicians whose careers are mainly in the rear-view mirror - they’re not going to have any prospects in a Boris Johnson government."

Many feel "out of sync" with the "modern Brexit-orientated Tory party", while "some feel under pressure in their constituencies, so there’s nothing to hold them back".

He added: "They are, some of them, prepared to put country before party. I think their hope is that Boris Johnson will pursue, as he said he will, an agreement, and so long as he does seek a deal with the EU, they are prepared to sit on their hands and behave and not cause trouble."

Business Secretary Greg Clark said while companies have largely kept faith in Britain in the three years since the referendum, that faith is beginning to vanish.

"In the last few months, I think since the since the 29th of March, there are more doubts being expressed in boardrooms as to whether this is ever going to be resolved, we need to prove them wrong," he said.

"And whatever happens in this leadership election, I hope whoever is prime minister will recognise the imperative to give that confidence."

Read more from the BBC's business editor Simon Jack.

The defence secretary, who has been supporting Mr Hunt in the race, tweets...

Beyond a single hustings held in Cardiff, issues relating to Wales have barely featured in the contest between Boris Johnson and Jeremy Hunt.

Read more here.

BBC Radio 5 Live

Image source, Getty Images

Either Boris Johnson or Jeremy Hunt must "go all out" to secure a "negotiated" Brexit, the director general for the British Chambers of Commerce, Adam Marshall, has said.

"It's always better to look for a negotiated solution than have a messy one," he told Wake Up to Money.

"There is a huge amount of frustration in our business communities and there are voices - there are people - who believe we need to somehow draw a line under the indecision and the impasse of the last three years.

"I'm afraid though that many of those people are looking for some form of certainty and I don't believe that a messy and disorderly exit would actually deliver them that certainty."

He said the government had not done enough to help businesses prepare for a no-deal Brexit.

"It's kind of like opening a trap door, only to discover that underneath there's quicksand because there would still be so many unresolved issues - both in our trading relationship with Europe, but also in terms of our links with the rest of the world," he added.

It is the Conservative Party's members who will decide whether it is Jeremy Hunt or Boris Johnson who gets to succeed Theresa May.

So, who are the grassroots members and what do they think on key issues, not least, of course, Brexit?

Find out more here.

Laura Kuenssberg
BBC political editor

In a few hours, two veteran Tory MPs will open an envelope that will contain the name of our next prime minister.

Some moments later they will deliver the congratulations or commiserations to Boris Johnson and Jeremy Hunt.

Shortly after that they will announce the result to the Conservative crowd, and more importantly of course, to the country.

The embedded expectation in Westminster is that the name will be Boris Johnson - unless the Tory party has been collectively deceiving itself in the past few weeks.

If it proves so, the triumph will be extraordinary. Not because of a journey Mr Johnson has been on in the last few weeks - the controversial former foreign secretary and London mayor started out as the frontrunner.

But because again and again, over many years, his own political accidents and behaviour would have ruled other politicians out.

Read more from Laura