Two phenomena hit Britain this past week: suffocating heat and Boris Johnson's swift ascendancy to prime minister. Both caused sleepless nights for some citizens.

"At one stage, we controlled two-thirds of the planet and now we've got Boris Johnson in charge? Great, we've done really well, haven't we?" said Steve Morris, visiting London with his family from Essex.

"It's just sad, isn't it?'' he said, before his wife piped in "I like him."

In a sudden change-up of prime ministers, with Theresa May's exit, Johnson is promoting unity, but facing a deeply divided Conservative Party and a country beleaguered by three years of political deadlock over Brexit.

In his first appearance in the House of Commons Thursday, waving his arms, bouncing in his shoes, jabbing at the opposition, Johnson peddled energy and optimism.

Johnson speaks in the House of Commons in London on July 25, 2019. (Reuters TV via Reuters)

The "future [will be] clean, green, prosperous, united, confident and ambitious. That is the prize, and that is our responsibility," he said.

Johnson is the third Tory PM in a row to govern Britain in the last decade, but after the sacking and resignations of more than half of May's cabinet, he's made clear his government will look very different.

Within hours of moving into 10 Downing Street, he'd fired 11 cabinet ministers. Five others quit, replaced with staunch Brexiteers comfortable with leaving the European Union without a negotiated deal.

In a hurry

BoJo, as is his nickname, is in a hurry to make good on his promise to take Britain out of the EU by Oct. 31, "no ifs or buts."

It's a high-stakes gamble, flying in the face of dire warnings from some business leaders and even some inside his party that "no deal" could be economic suicide for Britain.

The EU's chief Brexit negotiator, Michel Barnier, has already rejected reopening the existing departure deal, saying to do that was "unacceptable."

But the withdrawal agreement already on the table has been voted down three times in the British Parliament and Johnson says the EU has to find a way to make amendments.

Take the first letters of Johnson's promises of delivering Brexit, uniting the country, defeating the Labour Party and energizing Britain, and you get the word 'dude.' In a sendup of that, a tabloid invoked the Beatles' song Hey Jude. (Susan Ormiston/CBC)

"If it does not, we will have to leave the EU without an agreement," he said in the House of Commons during his first statement Thursday.

"We must turbo-charge our preparations to ensure that there is as little disruption as possible to our national life," the new PM said, counting down from 96 days before the October deadline.

The opposition Labour Party is adjusting to its new adversary across the Commons floor.

Taking Britain out of the EU with no deal is "the height of economic lunacy," Leader Jeremy Corbyn said in Commons this week, just before it rose for a summer recess.

"No one underestimates this country, but the country is deeply worried that the new prime minister overestimates himself."

Precarious grip on power

The Tories' grip on power is still precarious, no matter who's at the top.

Assuming the support of the Democratic Unionist Party, the government has a thin majority — just three MPs — and that could be whittled down further next week after a byelection.

"I think he can't go very long without a general election," said Bronwen Maddox, director of the Institute for Government, an independent think-tank in London.

"It really is very, very hard for him to get anything through, an ordinary budget or some of the very controversial legislation that is necessary for Brexit to happen."

Several former senior cabinet ministers have returned to the backbenches, with some promising to scuttle any attempts at exiting without a deal.

Supporters of Johnson gather outside 10 Downing Street and quote Winston Churchill, one of the new prime minister's political heroes, invoking courage. (Susan Ormiston/CBC)

"Many in the party are convinced they should even take the final step of voting down the government, voting down their own party rather than let that happen," said Maddox.

"I think it's very hard for him to govern in any sustained way. And it's really a question of when he picks his moment."

Many MPs on both sides of the House believe Johnson's high-stakes gamble is really a prelude to a general election later this year.

Lifting spirits — for now

Parliament does not resume until Sept. 3, and even if the opposition called for a no confidence vote on the first day back, an election could not happen before the end of October.

Johnson has adopted a more boisterous leadership of the Conservative Party, which is in the short term lifting spirits among some parliamentarians.

Gary Streeter, who's been a British MP for 26 years, assessed Johnson's performance on Day 1 as "brilliant" and done with "clarity, confidence."

Maddox thinks the party membership chose Johnson because of his optimism and "his sense that you can talk your way through Brexit," she said, "that if you just pour buckets of words over this and these are optimistic, cheerful words, that this will somehow be an antidote to what has gone before."

A Brexit deadline less than 100 days away will consume Johnson's summer. (Susan Ormiston/CBC)

Johnson is the opposite of dull, says Harry Mount, who edited The Wit and Wisdom of Boris Johnson and worked with him as a journalist.

"He is fundamentally unpredictable. Something could go very badly wrong," said Mount.

"Anybody would find it very difficult to get through the almost impossible setup of Brexit, but there is this little bit of magic in Boris. It is unlikely, but he could pull it off."

On Tuesday, as he won the leadership of the Conservative Party, Johnson was "en forme," spelling out his goals as leader: D for delivering Brexit, U for uniting the country and D for defeating the Labour Party's Corbyn. But, Johnson said with a grin, "some wag pointed out that spells 'dud.' " He added "E for energize, so it's dude," prompting guffaws in the audience of Tory members.

'World king'

It is local lore that as a child, Johnson said he wanted to be "world king."

Over 18 years of politics, he's risen and stumbled, famously, several times. After a particularly rough stint as foreign secretary, one conservative MP told Maddox: "Oh, Boris can't come back this time because you can't come back from humiliation."

Queen Elizabeth welcomes Johnson during an audience at Buckingham Palace on July 24, 2019, where she invited him to become prime minister and form a new government. (Victoria Jones/The Associated Press)

But, of course, he did, bowing his head slightly before the Queen this week as he took on the top political post in Britain.

"There is one Boris Johnson, the kind of Liberal, more cosmopolitan, including everyone kind of Boris Johnson we had a lot of during his time as mayor [of London]," said Maddox.

"But the other Boris Johnson who's got trapped by very hard words on Brexit and wanting to please the right of his party, that one is heading for a pretty immediate challenge, a battle with Parliament."