Boris Johnson won the race to become Britain's next prime minister on Tuesday, heading straight into a confrontation over Brexit with Brussels and parliament, as well as a tense diplomatic standoff with Iran. The former London mayor easily beat his rival, Foreign Secretary Jeremy Hunt, in a vote of members of the governing Conservative party.
He is expected to be confirmed as prime minister on Wednesday when his predecessor Theresa May formally tenders her resignation to Queen Elizabeth II.
US President Donald Trump was the first world leader to offer his congratulations, saying: "He will be great!"
It is a triumph for a man who has always wanted the top job. But Johnson, known for his jokes and bluster, is taking over at a time of immense political upheaval. Three years after the referendum vote to leave the European Union, Britain remains a member amid continued wrangling in a divided parliament on how to proceed.
'We'll get Brexit done'
Johnson led the 2016 "Leave" campaign and -- after May delayed Brexit twice -- insists the latest deadline must be kept, with or without a divorce agreement with the EU.
"We're going to get Brexit done on October 31," he declared in a speech to party members in London, after winning 66 percent of almost 160,000 votes cast.
However, Brussels says it will not renegotiate the deal it struck with May to ease the end of a 46-year partnership -- even after MPs rejected it three times.
EU negotiator Michel Barnier said Tuesday he wanted to work with Johnson "to facilitate the ratification of the withdrawal agreement and achieve an orderly #Brexit".
Ursula von der Leyen, who will take over as head of the European Commission on November 1, congratulated Johnson but warned of "challenging times ahead of us".
Although parliament dislikes May's deal, Johnson faces significant opposition from MPs to his threat to leaving with no deal, including from Conservative colleagues. Several ministers said they will not serve under Johnson, warning that severing ties overnight with Britain's closest trading partner is deeply irresponsible. Business leaders called on the incoming leader to get a deal, with the director general of the Confederation of British Industry, Carolyn Fairbairn, saying he "must not underestimate the benefits of a good deal".
Johnson insisted he would find a way through the deadlock: "Like some slumbering giant we are going to rise and ping off the guy ropes of self-doubt and negativity."
'Brilliant or a disaster'
Johnson said he would announce his top team in the coming days but Westminster is watching for an early challenge to his leadership. May's government has a majority of just two in the 650-seat House of Commons, even with an alliance with Northern Ireland's Democratic Unionist Party (DUP).
The main opposition Labour party is not expected to force a confidence vote this week -- but some in his own party have already tried.
Junior foreign minister Alan Duncan quit this week, revealing he had sought to force a vote on Tuesday but was blocked by Commons Speaker John Bercow. Other colleagues who do not agree with Johnson are willing to give him a chance to get a Brexit deal, at least over parliament's summer recess.
But if "no deal" looks likely in September, many MPs have vowed to stop him -- a move that could trigger an early election.
Labour has condemned Johnson, who was elected by party members representing just 0.3 percent of the electorate, as "out of touch". Labour leader Jeremy Corbyn challenged him to call an election. But both Labour and the Tories are struggling to appeal to a public deeply divided over Britain's future, facing a pincer movement from Nigel Farage's eurosceptic Brexit Party and the pro-EU Liberal Democrats.
Outside parliament, where pro- and anti-Brexit protesters gather daily, reaction to Johnson's win was mixed.
"It's the most we can hope for," said eurosceptic Michelle Pearce, 64, adding: "He'll be brilliant or a disaster."
Ruth Fryer, 66, wearing a "bin Brexit" badge, added: "He's a bit of a loose cannon and no one knows what he'll do."
Johnson's domestic battles might have to take a backseat during his first days in office as he manages tensions with Iran.
The Islamic republic seized a UK-flagged tanker in the strategic Strait of Hormuz last Friday -- two weeks after UK authorities detained an Iranian tanker off Gibraltar. The standoff comes amid escalating tensions between Iran and the United States over the former's nuclear ambitions.
Iranian Foreign Minister Mohammad Javad Zarif tweeted his congratulations to Johnson, saying: "Iran does not seek confrontation.
"But we have 1500 miles of Persian Gulf coastline. These are our waters & we will protect them."