Video report by ITV News Political Correspondent Paul Brand
After days of silence, Boris Johnson has launched his bid for the Tory crown with a warning to MPs they will "reap the whirlwind" if they try to thwart Brexit.
The main headline from his campaign launch speech was Brexit - telling Conservatives they faced "mortal retribution" from voters unless Britain leaves the EU on October the 31st.
Otherwise, there were plenty of earnest pledges to unify the country - but few jokes, little policy, and no answers to allegations about past drug use.
Later, there was a sharp aside from Sajid Javid at his campaign launch, telling those assembled that Mr Johnson is "yesterday's news."
Launching his leadership bid, Mr Johnson said he believed "maturity and a sense of duty will prevail" over Brexit.
"I think it will be very difficult for friends in Parliament to obstruct the will of the people and simply to block Brexit.
"I think if we now block it, collectively as parliamentarians we will reap the whirlwind and we will face mortal retribution from the electorate."
Boris Johnson's speech in full:
Meanwhile Labour said it would continue to fight to prevent a no-deal Brexit after the latest cross-party attempt by MPs to take control of Commons business was narrowly voted down.
In the Commons, the cross-party motion which would have enabled MPs to take control of the business of the House on June 25 was defeated by 309 to 298 - a majority of 11.
Ten Tories, including Ken Clarke, Sir Oliver Letwin, Justine Greening and Dominic Grieve, supported the motion but eight Labour MPs voted against.
Shadow Brexit secretary Sir Keir Starmer said it would haveacted as a "safety valve" enabling Parliament to pass legislation preventing the next prime minister from taking Britain out of the EU without a deal.
He said Labour would continue to work to find parliamentary mechanisms to ensure whoever succeeds Theresa May could not simply leave with no-deal in the autumn.
"This is a disappointing, narrow defeat. But this is just the start, not the end of our efforts to block no deal," he said.
"Any Tory leadership candidates should know that Parliament will continue to fight against no deal."
Mr Johnson, seen as the clear front runner in the contest, said it was essential that Britain was out of the EU by the end of October.
He insisted he was not aiming for no-deal, but said the Government had to show it was serious about leaving if it was to stand any chance of securing concessions from the EU.
"It is only if we have the guts and the courage to get ready for it (no-deal) that we will carry any conviction in Brussels to get the deal that we need," he said.
His comments prompted a warning from Chancellor Philip Hammond that it would be "impossible" to leave by October 31 as the EU would not re-negotiate and Parliament would not allow it.
"I don't think it's sensible for candidates to box themselves into a corner on this," he said. "I don't think it will be in our national interest that we drive towards this cliff-edge at speed."
ITV News Political Editor Robert Peston says that Boris Johnson remains the frontrunner in the race to become the next prime minister
Sajid Javid, the last of the 10 candidates to launch his campaign ahead of Thursday's first round of voting, dismissed Mr Johnson as "yesterday's news", saying the party needed to show it had changed.
His launch event, which began with a speech from Scottish Conservative Ruth Davidson, was pushed back significantly due to an unsuccessful Labour-led motion aimed at blocking no Brexit.
Mr Javid acknowledged the delay, claiming it was a Labour attempt to sabotage his bid to become PM.
He said: "When Labour tried to kybosh this launch of my leadership campaign, because the leadership campaign they fear the most, they failed and here we are."
During his speech, Mr Javid presented himself as a fresh candidate, someone unlike the others.
"If we're trying to connect with the next generation and move forward as a country then I think it's time for the next generation with a bold new agenda," the Home Secretary said launching his bid.
"That means understanding that we cannot call ourselves a 'one nation' party, if there are whole swathes of this country that don't think that we share their values and their needs."
Sajid Javid's speech in full:
At his launch event, Mr Johnson had to fend off a series of reporters' questions about his past character and record in office.
After Michael Gove's admission that he had taken cocaine in the past, Mr Johnson sidestepped a question as to whether he had also used the drug.
He acknowledged that his use of language - such as his description of Muslim women who wore the burka as letter boxes - sometimes resulted in "some plaster coming off the ceiling".
However, he rejected past charges of untrustworthiness levelled at him by colleagues and rivals.
Referring to his record as mayor of London, he said: "I do what I promise to do as a politician."
"We can't risk going with someone who feels like the short-term, comfort zone choice."
Meanwhile Mr Johnson officially launched his leadership campaign after days of staying silent, setting out his vision for a swift exit from the European Union, with a promise to end the "morass" over Brexit.
At his event launch, which began with a promotional video and a speech from Attorney General Geoffrey Cox, Mr Johnson said he doesn't "want a no deal outcome" but thinks it is right to "prepare for that outcome".
The former foreign secretary insisted that it is essential that Britain finally leaves the EU at the end of October to prevent the mood of "disillusion, even despair" in the country from spreading.
Shortly after Mr Johnson began speaking, heckling from the street outside the venue was audible in the room, with cries of "B******* to Boris" and "No to Brexit" echoing in the room.
Inside however was a different story, with several big name Tories, including Jacob Rees-Mogg, Iain Duncan Smith and Liz Truss, turning out to support the former London mayor.
Other Tories who backed Mr Johnson by attending his event were Nadine Dorries, Priti Patel, and Chris Grayling, along with his brother Jo and father Stanley.
In his speech Mr Johnson warned failure that to honour the referendum vote risked handing power to Jeremy Corbyn and Labour at the next general election.
"After three years and two missed deadlines, we must leave the EU on October 31," he said.
"Delay means defeat. Delay means Corbyn. Kick the can and we kick the bucket."
He added: "The best way to avoid a no deal outcome, the best way to avoid a disorderly Brexit of any kind is to make the preparations now that enable us to leave in a managed way.
"But above all, if we make preparations now we will carry the conviction, with our friends and partners, that we are indeed able to make such an exit if we really have to."
Ending his speech, Mr Johnson said: "To sum up my mission in a sentence: what I want to do now, with your help, is to do for the whole country what we did in London - releasing the creative energies of our country and its people and healing its divisions."
Attendees at the launch were offered "Boris bacon butties" and "Boris eggs Benedict" inside the venue, they were also invited to wear "Back Boris" badges.