Boris Johnson has attempted to put an optimistic stamp on the start of his premiership as he made his first appearance as Prime Minister at the Commons.
The PM used his first Commons statement to set a promise of making the UK the "greatest place on earth" by 2050.
He said: "Our mission is to deliver Brexit on October 31 for the purpose of uniting and re-energising our great United Kingdom and making this country the greatest place on earth.
"And when I say the greatest place on Earth, I'm conscious that some may accuse me of hyperbole, but it's useful to imagine the trajectory on which we could now be embarked.
"By 2050 it's more than possible that the United Kingdom will be the greatest and most prosperous economy in Europe at the centre of a new network of trade deals which we have pioneered."
Mr Johnson insisted the UK must exit the EU by October 31, stating: "I, and all ministers, are committed to leaving on this date. Whatever the circumstances.
"To do otherwise would cause a catastrophic loss of confidence in our political system.
"It would leave the British people wondering whether their politicians could ever be trusted again to follow a clear democratic instruction."
He added: "I would prefer us to leave the EU with a deal - I would much prefer it.
"I believe that it is possible even at this late stage and I will work flat out to make it happen.
"But certain things need to be clear.
"The Withdrawal Agreement negotiated by my predecessor has been three times rejected by this House.
"Its terms are unacceptable to this Parliament and to this country."
The new PM was surrounded by a brand new team of ministers, including arch-Brexiteer Jacob Rees-Mogg and Vote Leave veterans Priti Patel and Dominic Raab in Downing Street this morning.
Mr Johnson was flanked by Chancellor Sajid Javid on his left and Cabinet Secretary Mark Sedwill to his right.
The new Conservative leader told the room it was "wonderful to see this new team assembled here" which respects the "depth and breadth of talent in our extraordinary party”.
"As you all know we have a momentous task ahead of us, at a pivotal moment in our country's history," he added.
"We are now committed, all of us, to leaving the European Union on October 31 or indeed earlier - no ifs, no buts.
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"But we are not going to wait until October 31 to get on with a fantastic new agenda for our country, and that means delivering the priorities of the people."
The meeting came after a night which saw more than half of Mrs May’s Cabinet either quit or sacked by Mr Johnson.
The cull prompted speculation that the PM could hold a snap general election after MPs return in September - once they have finished their summer break which starts on Friday - to try to break the Brexit deadlock.
Mr Rees-Mogg, who led the pro-Brexit Tory European Research Group (ERG), denied there had been a "Leave" takeover at the top of the new administration.
"Boris is bringing the country together, the party together, through his Cabinet appointments. It is not a Leave takeover Cabinet by any means," he told Sky News.
However he issued a sharp warning to disgruntled former ministers plotting to thwart Mr Johnson's Brexit plans that it was hard to see how they could succeed.
"The Withdrawal Act means that the default position is that we leave on October 31. That would have to be changed to stop the law taking its course," he said.
"Parliament would have to change the law and it is hard to see how that will happen.”
Mr Johnson expected to continue with middle-ranking and junior ministerial appointments throughout the day.