Boris Johnson has as expected beaten Jeremy Hunt to become the leader of the Conservative Party.
Mr Johnson won the ballot of Tory members by a landslide margin of 2-1, securing 92,153 votes compared to Hunt’s 46,656.
He will become prime minister tomorrow.
The new Conservative Party leader used his victory speech to promise that he would meet the October 31 Brexit deadline with a “new spirit of can do”, releasing the country’s “guy ropes of self-doubt and negativity”.
He said it was an “extraordinary honour and privilege” and insisted that “we are going to unite this amazing country and we are going to take it forward”.
At the leadership announcement event in central London, Mr Johnson said: “We are going to get Brexit done on October 31, we are going to take advantage of all the opportunities that it will bring in a new spirit of can do.
“And we are once again going to believe in ourselves and what we can achieve, and like some slumbering giant we are going to rise and ping off the guy ropes of self-doubt and negativity.”
Improved education, infrastructure, more police and full-fibre broadband are among the ways Mr Johnson said this would be achieved.
But Mr Johnson’s main task will be fulfilling his “do or die” promise to deliver Brexit on October 31, which he has said he will do with or without a deal.
Theresa May, who will resign as Prime Minister tomorrow, offered her congratulations but stressed that Mr Johnson should work “to deliver a Brexit that works for the whole UK”, a clear warning against a no-deal departure.
She promised Mr Johnson “my full support from the back benches”.
US President Donald Trump, who repeatedly praised Mr Johnson even while visiting Mrs May, said he would be a “great” prime minister.
Michel Barnier, the EU’s chief Brexit negotiator, said Brussels looked forward to working with the new prime minister on ratifying the Withdrawal Agreement — the deal which Mr Johnson has already declared dead.
Mr Barnier said the EU was ready to “rework” the Political Declaration on the future relationship.
Mr Johnson will be appointed as prime minister on Wednesday by the Queen after Mrs May formally resigns from the office.
He secured 66.4% of the votes to defeat Mr Hunt in the leadership ballot.
Despite the resounding victory, Mr Johnson’s share of the vote was slightly lower than that achieved by David Cameron in the 2005 Conservative leadership election, when he took 67.6%.
Mr Johnson faces a daunting in-tray at Number 10, not only the tight Brexit deadline but also 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.
Labour leader Jeremy Corbyn urged Mr Johnson to call a general election.
He said: “Boris Johnson has won the support of fewer than 100,000 unrepresentative Conservative Party members by promising tax cuts for the richest, presenting himself as the bankers’ friend, and pushing for a damaging no-deal Brexit. But he hasn’t won the support of our country.”
The end of the leadership race marks the beginning of many challenges to come.
Here is a look at the daunting in-tray facing Mr Johnson when he enters Number 10 on Wednesday.
Finding a way to succeed where Theresa May failed, by getting a Brexit deal through Parliament, will be the most immediate political challenge.
Unless a snap general election is called to elect a new House of Commons, the incoming leader will face the same parliamentary difficulties that scuppered Mrs May’s attempts to build a coalition behind her proposals.
Alternatively, a new premier could pursue a no-deal policy and allow the UK to leave on October 31 without a formal agreement - although MPs may take steps to prevent that happening.
Either way, the new prime minister will have to find a way to reunite a Tory party which has splintered over the issue and counter the threat posed by Nigel Farage’s Brexit Party, which has sucked support away from the Conservatives.
Brexit has reignited the Scottish National Party’s push for independence.
Scotland voted to remain in the European Union and First Minister Nicola Sturgeon has said she wants another referendum on independence by 2021 if the country faces being taken out of the bloc.
In Northern Ireland, which also voted to remain in the EU in 2016, Sinn Fein has repeatedly called for a border poll to be conducted on whether there should be reunification with the Republic of Ireland.
Under the terms of the 1998 Good Friday peace agreement, the UK Government is obliged to call a vote on the constitutional issue if there is evidence of a change in public opinion in Northern Ireland in favour of Irish reunification.
Fears of a descent into an all-out conflict between Iran and the West reached new heights when a British-flagged tanker was seized by Tehran.
The seizure of the Stena Impero by Iranian Revolutionary Guards in the Strait of Hormuz was condemned by Foreign Secretary Jeremy Hunt as an “act of state piracy”.
With Downing Street being accused of having “dropped the ball”, the Government was to attempt to assembling a European-led maritime mission to protect ships through the key route
Tehran was suspected of retaliating over the detention of the Iranian supertanker Grace 1, held in Gibraltar after being detained in an operation involving British Royal Marines.
The UK is at odds with its US allies over the Iran nuclear deal, but shares some of Washington’s concerns about Tehran’s wider activities in the Middle East.
With Mr Trump ramping up the US military presence in the area, the new prime minister could be forced to confront major decisions about war and peace early in their tenure.
However, Mr Johnson backed diplomatic efforts and ruled out backing the US in any conflict against Iran when making his leadership pitch.
Maintaining a grip on power
The door to Number 10 may be opening for Mr Johnson, but there are real questions about how long he can keep the keys.
He will command a working majority of just two after Dover MP Charlie Elphicke had the Conservative whip suspended when he was charged with sexually assaulting two women.
And that wafer-thin majority is with the backing of the DUP.
This may further slip to just one if the Tories lose the Brecon and Radnorshire by-election on August 1.
There they are fielding Chris Davies, who was ousted from the seat by a recall petition triggered after he was convicted of submitting false expenses claims.
To add to the pressure, the so-called Gaukeward squad of Tory heavyweights are eyeing a rebellion against any attempt to depart the EU without a deal.
Their namesake, Justice Secretary David Gauke, has given notice that he will resign rather than serve under Mr Johnson, as has Chancellor Philip Hammond.
Sir Alan Duncan quit as Foreign Office minister on Monday and education minister Anne Milton resigned less than an hour before Mr Johnson’s victory was announced.
And any attempt he makes to force through a no-deal Brexit against the desires of MPs could face a legal challenge, with Tory former PM John Major threatening such a move.
A post-Brexit trade deal is one of the key prizes sought by the UK after leaving the EU, but negotiations are likely to run into difficulties over agricultural standards - with political rows over chlorine-washed chicken and hormone-treated beef - and Mr Trump’s “America first” approach to international affairs.
Managing the special relationship will be especially challenging for the next PM following a fraught few weeks of diplomatic drama which led to the resignation of the UK’s ambassador to the US, Sir Kim Darroch.
Unless Mrs May makes an appointment in her final hours, Mr Johnson will soon have to make the key decision on who should be Britain’s representative in Washington.
The tensions caused by China’s rise as an economic and political powerhouse are felt across the West, with the row over whether to allow Huawei to contribute to the UK’s 5G network a symptom of wider unease.
Mr Trump’s US has adopted a tough public approach to China - banning Huawei and slapping tariffs on steel and other imports - while the UK has sought to build a “golden era” of relations with Beijing.
Culture Secretary Jeremy Wright said as recently as Monday that the Government is “not yet in a position” to form a decision, saying clarity is being sought on the implications of US actions against the firm.
Pressure on the new PM from Washington, a final decision on Huawei and disputes over Beijing’s territorial claims in the South China Sea could lead to a rocky period for the UK-China relationship.
The issue which, more than any other, derailed Mrs May’s 2017 general election campaign, her successor will have to come up with a system to cope with the rising costs of the UK’s ageing population.
A Green Paper setting out proposals on how to fund the system has been repeatedly delayed and the issue is politically toxic, with any suggestion of paying for care out of a person’s estate after they die liable to be condemned as a “death tax” by critics, while hiking income tax or national insurance could also be unpopular.
Successive governments have failed to get to grips with the nation’s housing shortage and the issue is likely to feature heavily in the Tory leadership contest.
The Government has a goal of building 300,000 new homes a year by the mid-2020s.