Boris Johnson will today abandon his campaign bunker and subject himself to the full force of the media glare with a stark warning for his party: delay Brexit and we die.

The frontrunner’s campaign launch will be the biggest event of the contest so far as the former Foreign Secretary finally opens himself up to the penetrating questions of the Press and broadcasters.

One view is that Mr Johnson has done so well thus far because he has said very little. Today that changes.

His opponents will doubtless hope that scrutiny will begin to expose his shortcomings and reveal his lack of focus and seriousness. His supporters believe the London MP will show his time has come to lead Britain through and beyond Brexit.

In the same central London venue Jeremy Hunt launched his bid on Monday, Mr Johnson will seek to portray himself as a prime minister, who can not only deliver a successful departure from the EU but also help Tory colleagues keep their seats at the next General Election.

Mr Johnson will say: “Now is the time to unite this country and unite this society and we cannot begin that task until we have delivered on the primary request of the people; the one big thing they have asked us to do. After three years and two missed deadlines, we must leave the EU on October 31.

“We simply will not get a result if we give the slightest hint that we want to go on kicking the can down the road with yet more delay. Delay means defeat. Delay means Corbyn. Kick the can and we kick the bucket,” he will declare.

The former Cabinet minister will say with every week and month that goes by in which the Government fails to deliver on its promise, the further the Tories will alienate not just their natural supporters but anyone who believes politicians should deliver on their promises.

Stressing his ability to take on Jeremy Corbyn, the former London May will say: “We cannot let Labour anywhere near Downing Street and I would remind you the last time I faced an emanation of that Marxist cabal I defeated him when the Conservatives were 17 points behind in London. We can do it again.”

Yesterday at her own campaign launch, fellow Brexiteer Andrea Leadsom set out her plan for a "managed exit," saying leaving the EU on October 31 was, for her, a "hard, red line".

The former Commons Leader insisted it was impossible for MPs to prevent a no-deal exit as this was the legal default position but she argued by “putting forward sensible measures that Parliament will agree to, and the EU will also find very sensible, that have already been agreed in the Withdrawal Agreement, we will have success".

But it was a few hours later at a parliamentary press gallery lunch when Ms Leadsom committed news.

After a somewhat playful presentation to a room full of journalists in which she held up a sign “Bollocks to Bercow,” illustrating her less-than-friendly relationship with the Commons Speaker, the Northamptionshire MP was asked about Scotland and the prospect of a second vote on independence.

To raised eyebrows, she declared: “Never say never.” Eyebrows were raised because the official Government line is to say no to Nicola Sturgeon now and for the rest of the Parliament ie to May 2022.

But Ms Leadsom explained: “The reason I say 'never say never' is because I do not think that there should be another independence referendum in Scotland, I do not think it's in their interest, but, on the other hand, I am a big believer in devolution.

"So, what I just want to say is I am not going to stand here and utterly rule it out because that is disrespectful. But I would very strongly fight against a second referendum, which I don't think is in the interest of Scotland and it's definitely not in the interests of the UK.”

However, the political damage appeared to have been done.

The SNP’s Joanna Cherry, who was at the lunch, described the Tory candidate’s answer as “fascinating” and said she looked forward to the comments of Ms Leadsom’s Scottish Conservative colleagues.

It did not take long. One Scottish Conservative MP, when he was told about what Ms Leadsom had said, declared: “You are f*****g kidding me.”

Ross Thomson, the MP for Aberdeen South, was more polite but equally dismissive, saying: "I don't think any Scottish Conservative could back a candidate who won't be firm on saying no to indyref2. Never say never[again] is just a bad Bond film."

Ian Blackford, the Nationalist leader at Westminster, happily seized on Ms Leadsom’s remarks, saying she was right and it would be a “democratic outrage for the Tories to stand in the way of democracy”.

Matt Hancock, at 40 the youngest contender, stressed how he would put his Brexit plan to the Commons within days of entering No 10 and before the summer recess in July. The UK Health Secretary claimed that having a Commons mandate would result in co-operation from Brussels to put a time limit on the backstop.

Sajid Javid, who also launches his campaign today, insisted his focus was on getting a deal but admitted that if by October 31 the choice was between a no-deal outcome and no Brexit, he would choose the former.

The Home Secretary also made clear he was “very open-minded” about having different migration rules for different parts of the UK. He noted how the median salaries of people in London were “higher than they are, say, in Scotland”.

But as the Tory race gathered pace, there was a not-so-gentle reminder from Brussels about what the victor faced.

Jean-Claude Juncker, the outgoing European Commission President, stressed how the Withdrawal Agreement was “not a treaty between Theresa May and Juncker; this a treaty between the United Kingdom and the European Union".

He added: “We can have some clarifications, precisions, additions to the Political Declaration concerning the future of our organisations. The Withdrawal Agreement will not be renegotiated."

Yesterday evening in the unconventional setting of a large tent on London’s South Bank, Rory Stewart launched his bid for the Tory crown urging his rivals to face the reality of the Brexit situation.

Supported by Tory grandees Ken Clark and Nicholas Soames, he attacked those leadership rivals advocating a no-deal Brexit, accusing them of peddling "fairy stories".

"It is not just no to a deal. It is no to everything. It is no to Europe, it is no to trade, it is no to Parliament, it is no to reality. We are not a 'no' country," he declared.

Addressing what he saw as the threat to the Union from Brexit, the Scot said he was “terrified about the way in which we keep this miracle, the United Kingdom, together”.

The International Development Secretary argued a no-deal Brexit would give an “extraordinary gift to Nicola Sturgeon” while a second EU referendum would give a “huge gift to people who want to rerun the independence referendum in Scotland”.

He added: “So this whole thing is shaking this very precious entity[which] is the reason for our success in the world.”