The BBC asked members of the public in Wales what they thought of the UK's new prime minister. This is what they had to say:

At her final cabinet meeting, ministers presented Theresa May with gifts of a handbag and a necklace.

They clapped and banged the cabinet table in a show of appreciation. A Downing Street source described it as a "genuinely nice ending".

The gifts - a black handbag from Liberty and a Lalique necklace - were bought with a whip-round and presented by environment secretary Michael Gove.

Jair Bolsonaro - Brazil's right wing president - has offered his congratulations to Boris Johnson on social media.

Mr Bolsonaro tweeted Mr Johnson had been elected on the basis he would "respect the designs of the British people", adding the UK could count on Brazil in its pursuit of free trade, prosperity and the defence of freedom and democracy.

This is how leaders of the UK's other political parties with MPs reacted to Mr Johnson's victory:

Jeremy Corbyn (Labour): "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."

Jo Swinson (Lib Dems): "Boris Johnson has finally got his hands on the keys to Number 10, but he has shown time and time again that he isn't fit to be the prime minister of our country. Whether it is throwing people under the bus or writing a lie on the side of one: Britain deserves better than Boris Johnson."

Caroline Lucas (Green Party, no comment from leaders): "Around 100,000 Tory party members have inflicted on us a prime minister with a record of bigotry, racism, lying and incompetence. This is not democracy This is not in our name."

Anna Soubry (The Independent Group for Change): "It's a very bleak day for our country. It's as stark as that. He's called the great charlatan for good reason. And he is absolutely shameless in his ability to shift his position."

Nicola Sturgeon (SNP): "I congratulate Boris Johnson on his election as Tory leader and I will do everything possible to ensure that he respects Scotland's views and interests. However, I have profound concerns about the prospect of his premiership and it would be hypocritical not to be frank about these."

Adam Price (Plaid Cymru): "During the most serious political crisis in decades, a clown is set to become prime minister. But this is no joke. People will soon realise, this isn’t as good as it gets. By electing Boris Johnson, the question of Welsh independence is not of ‘if’, but ‘when’."

Arlene Foster (DUP): "Congratulations to Boris Johnson on becoming Conservative Party Leader. Look forward to discussing our shared objectives of strengthening the Union, delivering Brexit and restoring devolution."

Michelle O'Neill (Sinn Fein): "We will continue to work with the Dublin government and the EU27 to protect Ireland from the catastrophic impact of the reckless Brexit being pursued by Boris Johnson and the hard Brexiteers."

Asked if the Labour Party could work with Boris Johnson to approve a Brexit deal, Labour's shadow chancellor John McDonnell tells the BBC: "No, I don't think so."

He says: "I think he is quite serious about a no-deal Brexit and we have to oppose that.

"I can’t see Boris Johnson negotiating any deal that will protect jobs and the economy."

Mr Johnson should call a general election instead, he says.

"He’s been elected by less than 100,000 party members. Now is the time he should seek a democratic mandate and go to the people and have a general election. That would help us determine the Brexit issue as well."

Mr McDonnell says although Labour wants a referendum and would campaign to remain in the EU, it is "very difficult to see" how they could get backing for it in Parliament.

It is "probably easier" to get through a vote of no confidence in Mr Johnson if he tries to force the UK to leave the EU without a deal on October 31.

"It will depend on those Tory MPs who are saying they will stand strong against no deal, standing strong," he says.

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Former deputy prime minister Michael Heseltine tells the BBC that Boris Johnson is now "in hock" to the Conservative Party's Eurosceptic wing, making it hard for him to take a more moderate position in power.

"He has, if you like, fed the sharks - a very dangerous thing to do," he says.

Having sought the support of the Eurosceptics, Lord Heseltine says Mr Johnson faces pressure to give them cabinet appointments "which will alienate the centre ground", or he risks losing their backing.

But if Mr Johnson does face a no-confidence vote, Lord Heseltine says, "he may win because people don't want a general election".

"We’re in for a period of considerable instability and uncertainty," he says.

"The problem with that, of course, is that industry has stopped investing. Industrialists are just sitting on their hands; overseas investors are saying what the hell are we supposed to do?"

Image source, PA Media

One of the first commitments Boris Johnson made in the leadership campaign was to raise the 40% income tax threshold from £50,000 to £80,000.

The Institute for Fiscal Studies (IFS) has said this will cost around £9bn, external and constitute a "major change to our income tax system".

He has said, however, that his first priority will be to raise the threshold from which employees pay national insurance. The IFS has said this will cost £3bn for each £1,000 that it is raised.

He has also pledged to increase the national minimum wage, find more money for public sector workers and review "sin taxes" such as the sugar tax.

Scottish independence campaigners gathered in Glasgow to protest against the appointment of Boris Johnson as prime minister.

People carried Saltire flags and held signs saying: "Boris No! Independence Yes!"

Gary Kelly, an organiser from the pro-independence group All Under One Banner, said: "We knew it was going to be a prime minister Scotland wouldn't want."

Former Scottish politician Tommy Sheridan spoke to the crowd and criticised Mr Johnson's election by "less than 0.5% of the registered voters in the UK".

"The overwhelming majority of people here today are here because they're angry. They're angry that they weren't asked whether Boris Johnson should become the next prime minister."

One Labour Party member explained to BBC Radio 5 Live why they thought Mr Johnson would come unstuck against Jeremy Corbyn in a general election:

Image source, Getty Images

Boris Johnson has not committed to the target pursued by Theresa May of lowering net migration to below 100,000 per year.

Instead of pledging a target on numbers, he says the government will gain more control over immigration after Brexit by using an Australian-style points-based system.

You can read BBC Reality Check's analysis of how such a system might work here.

He has also said he wants to block the ability of people to claim benefits immediately after arriving in the UK, and has previously favoured an amnesty for long-time illegal immigrants.

Boris Johnson needs to show "maturity" after being elected new Conservative leader, Wales' First Minister Mark Drakeford has said.

Welsh Labour's leader said he hoped Mr Johnson would show "strategic thinking and honesty needed to meet the challenges he, and we all, face".

But Plaid Cymru leader Adam Price said the Conservative Party had elected a "clown".

"This is no joke. People will soon realise, this isn't as good as it gets. By electing Boris Johnson, the question of Welsh independence is not of 'if', but 'when'," said Mr Price.

Read more Welsh reaction to Mr Johnson's appointment here.

Image source, Reuters

Boris Johnson will become the 14th prime minister to serve under Queen Elizabeth II, and the 20th to have gone to school at Eton College.

Aged 55, Mr Johnson is two years older than Margaret Thatcher when she took office.

Born in New York, he will become the second PM to be born outside the UK - the first was Andrew Bonar Law (1922-23), who was born in Canada.

There's also an echo of the 1920s in his constituency majority of 5,034 - the lowest of any serving PM since Ramsay MacDonald in 1924.

Image source, PA Media

Sinn Fein deputy leader Michelle O'Neill says her party will work to protect the peace process and Good Friday Agreement in all its parts, including the commitment to calling a referendum on Irish Unity.

"The British government has responsibilities and commitments under the terms of the Good Friday Agreement and we will hold them to account," she said.

"We will continue to stand up for Irish interests, for the majority of citizens in the north who voted on a cross-community basis to remain within the EU.

"We will continue to work with the Dublin Government and the EU27 to protect Ireland from the catastrophic impact of the reckless Brexit being pursued by Boris Johnson and the hard Brexiteers."

Some of Jeremy Hunt's supporters have been tweeting their congratulations to Mr Johnson, as well as voicing their pride at being part of the losing campaign.

Image source, Conservative Party

Mark Spencer has been relatively under the radar since he first walked down Whitehall as the MP for Sherwood in 2010.

The 49-year-old's appointment as chief whip was Boris Johnson's first following his victory in the Conservative Party leadership contest, and has generally been well received by colleagues.

Long-serving Tory Sir Nicholas Soames said: "Absolutely delighted to hear of the appointment of Mark Spencer as chief whip.

"A really excellent sane and wise choice."

Meanwhile, business minister Andrew Stephenson added: "Congratulations to the new chief whip - the man who taught me how to 'put a bit of stick about'."

Away from politics, Mr Spencer is a farmer and businessman whose family have lived on the edge of Nottinghamshire for four generations.

He often plays in goal for the Conservative MPs when they play football against a team of journalists at the party conference each year.

Image source, EPA

Here’s where we are right now, with Boris Johnson set to become the UK’s next prime minister after receiving two-thirds of the votes in a ballot of party members.

He decisively beat Foreign Secretary Jeremy Hunt - who earlier admitted his decision to vote Remain in the 2016 referendum had proved an insurmountable hurdle with members.

Mr Johnson will officially take office tomorrow and begin making appointments to his cabinet – but it is already confirmed that Nottinghamshire MP Mark Spencer will become his chief whip.

A number of other Conservatives, however, have ruled out serving under Mr Johnson because of his pledge to deliver Brexit by 31 October, even without a withdrawal deal.

Education minister Anne Milton resigned just before the result was announced – whilst Justice Secretary David Gauke, Chancellor Philip Hammond and International Development Secretary Rory Stewart had already indicated they will be returning to the backbenches.

Mr Johnson received a hearty welcome from Tory backbenchers when he addressed them earlier, delivering a message the party needs to “unite and win”.

Image source, Getty Images

Scottish Conservative leader Ruth Davidson says she has been "perfectly open and honest" with Boris Johnson that "he wasn't my choice for leader".

Ms Davidson, who backed Sajid Javid, tells BBC Scotland: "He's prime minister, he's won it fair and square, and most fair-minded Scots across the country will judge his premiership by his actions in office, as I will."

She says he now faces the "enormous task" of delivering Brexit and he has a "very small window to do that".

"I hope he can, I hope he can come back from Europe with a deal on the table," she says.

David Frost, former ambassador, has been appointed as Boris Johnson’s EU Sherpa.

Previously a special adviser to Mr Johnson at the Foreign Office and Europe Director, he will take on the role performed by Olly Robbins under Theresa May.

Image source, Reuters

With Boris Johnson having been critical of the Russian regime, the media there is repaying the favour with a sceptical response to his appointment as prime minister.

Reports highlight what Russians see as his eccentricity, his tabloid reputation for affairs and his perceived hostility.

State TV's Rossiya 24 said he blamed Russia for an attack on a UN convoy in Syria "without evidence", accused the country of interfering in elections and called on the international community to increase pressure on Russia.

"At the same time, he called on foreign colleagues not to demonise Russia. Apart from that, he repeatedly openly expressed pride in his Russian roots and name. In Moscow, he even called himself a confirmed Russophile."

It all adds up to a "contradictory position", the channel reported.

State TV's Channel One said Theresa May "failed miserably and dragged down her party's rating" but Mr Johnson is "remembered not so much for his political deeds, as much as for - mildly put - oddities".

Leading MP Konstantin Kosachyov said: "It's unlikely to be fun," adding that he expected "the same graveyard depression" in Russia-UK relations.

And for Kremlin pool correspondent Dmitry Smirnov, Mr Johnson is "an unprincipled and irresponsible populist, elected because of the sheer lack of alternatives".