Having fought her way to the top of British politics, new Prime Minister Theresa May will face an even tougher battle in power: plotting a divorce from the European Union that she once opposed but now says must not be halted.
The fate of the post-World War Two project of European integration, and even of the United Kingdom itself, will depend on May's rapport with another pastor's daughter who climbed to the summit of a conservative party: Germany's Angela Merkel.
May's biggest immediate decision will be when to trigger formal exit proceedings. It is a call she will have to make while also facing an economy under extreme strain, deep division in the ruling party and potential demands from nationalists in Scotland for a referendum on independence.
Despite having campaigned to remain in the EU before the June 23 Brexit referendum, May, 59, said on winning the Conservative Party leadership there would be no turning back: "Brexit means Brexit and we are going to make a success of it."
The Brexit vote thrust Britain into political crisis with both major parties in leadership battles and investors left guessing about the future relationship with the EU.
She described her job as steering Britain through treacherous economic and political uncertainties, negotiating a proper exit and forging "a new role for ourselves in the world".
As Britain's second female prime minister, May has prompted comparisons with "Iron Lady" Margaret Thatcher, who governed from 1979 until 1990 and was no stranger to doing battle in Europe. May's six years in charge of the cabinet's law-and-order portfolio was the longest tenure for a century in what is widely seen as one of the government's toughest jobs.
The Sun newspaper, Britain's biggest selling daily, cast May as "The Iron Mayden", the new "Mrs T".
Veteran Conservative lawmaker Ken Clarke, who served as a minister under Thatcher, was caught on a live microphone in a TV studio this month describing May as "a bloody difficult woman".
May took the remark as a badge of honor, repeating it to lawmakers at a party leadership hustings, and adding that the next person who would find out just how difficult she was would be European Commission head Jean-Claude Juncker.
Despite calls from many European leaders that Britain start the divorce process as soon as possible, she has been firm that Britain will not rush to trigger Article 50 of the Lisbon Treaty, which starts a two-year countdown to exit.
"There should be no decision to invoke Article 50 until the British negotiating strategy is agreed and clear -- which means Article 50 should not be invoked before the end of this year," May said on June 30 when she launched her bid to succeed David Cameron, who announced his resignation after the Brexit vote.
She will be up against the clout and stamina of Merkel, who in 10 years as chancellor has regularly outlasted other EU leaders at late night meetings.
The crucial issue is balancing the desire of British voters to restrict immigration from other EU countries with the need of British business to keep access to the European common market.
May has a record of negotiating compromises with the EU. But Merkel, like other European leaders, has said there can be no "cherry picking" by Britain: it must accept free movement if it wants free trade.
The Oxford University-educated daughter of a Church of England vicar, May is highly regarded among European officials, who say she knows Brussels well and is always well prepared.
"She won't be an easy partner for the EU," said one senior EU official familiar with negotiations in which May has taken part, adding that she does not change her tune easily. "She's been extremely consistent, very persistent."
Colleagues say May, who became a lawmaker in 1997, shuns the "old boys club traditions" of parliament, preferring to spend any free time she has with her husband of 36 years, Philip, than go drinking in parliament's bars.
That is a relief for her party and the wider country after a Brexit debate and bitter post-referendum leadership contest dominated by infighting among male Conservatives who had been friends and rivals since boarding school and university.
"Frankly at the moment most people in this country would be quite pleased at the thought they've got a prime minister who doesn't gossip, doesn't do back-stabbing," Anne Jenkin, a Conservative member of the upper house who with May co-founded the group Women2Win in 2005 to try to get more women in to parliament, told the BBC.
Former Belgian interior minister Joelle Milquet said that while she did not share May's views on Europe, she found her to be "pleasant and warm" on a personal level, and someone who defends her position "with panache".
"She is a very level-headed woman, who is a good judge of things," she told Reuters. "All woman who reach a certain level in politics have plenty in common: they've had to fight, they've had to win respect, prove themselves 10 times as much as any man, they've had to put up with macho attitudes, so by necessity they're tough."
Despite similarities to fellow pragmatist Merkel, May has shunned comparisons with other female leaders.
"I've said I wasn't a showy politician and the other thing I've never done as a politician is try to compare myself to any other politician," she said at her campaign launch when asked if she saw parallels with her soon-to-be EU adversary.
"My pitch is simple - I'm Theresa May and I think I'm the best person to lead this country."
Soon after the Brexit vote, May demanded the government scrap its plan for a budget surplus by 2020, easing the austerity economics that were the bedrock of David Cameron's six years in power. She has promised to narrow the pay gap between bosses and workers and produce a fairer economy.
"The only surprise is that there is so much surprise in Westminster about the public's appetite for change," May told supporters and journalists in Birmingham on Monday.
"And make no mistake, the referendum was a vote to leave the European Union, but it was also a vote for serious change."
As interior minister, she opted back into a European arrest warrant system and cross-border information sharing despite Britain's 'opt out' on EU justice and home affairs policy.
In brokering those 'opt-ins', the senior EU official said: "She took a great part in the negotiations herself, she didn't rely on officials ... She has very obvious negotiating skills."
Timothy Kirkhope, a Conservative member of the European Parliament and the party's spokesman for home affairs there, said May had picked out the best bits for Britain.
"It was very matter of fact, businesslike," said Kirkhope, also a former junior minister in Britain's interior ministry.
"She has this ability to not let on too much where her negotiations might be going ... If she were a poker player I would probably have some reservations about taking her on."
May, who lost both her parents while in her twenties, describes herself as a practicing Christian and a fan of cooking, owning more than 100 cookery books.
She gets up early and spends time in the gym as he health is important to her, said one Conservative lawmaker who has worked closely with May.
May has Type One diabetes and needs insulin injections several times a day, once describing in an interview how she been forced to break strict parliamentary rules on not eating in the chamber during a particularly long debate.
"I had a bag of nuts in my handbag and one of my colleagues would lean forward every now and then, so that I could eat some nuts without being seen by the Speaker," she said.
Despite criticism for a poster campaign telling illegal immigrants to go home, May has largely won plaudits from both colleagues and political opponents during her six years as interior minister. She has pushed through measures including reforms of the police and moves to tackle modern slavery.
Damian Green, a Conservative lawmaker who worked under her as a junior minister, described her as "completely Stakhanovite" -- a Russian term for someone with legendary capacity for hard work.
"She had a very clear sense of long-term direction as well as the capacity to do the detail," Green told Reuters. "She wasn't to be pushed aside or pushed about."