As a child, Liz Truss marched in demonstrations against Conservative Prime Minister Margaret Thatcher. As an adult, she came to admire Britain’s first female leader — and now she is about to enter No. 10 Downing St. with a Thatcherite zeal to transform the U.K.

Truss, Britain’s foreign secretary, was named winner Monday in the contest to replace the scandal-plagued Boris Johnson as Conservative Party leader and the country’s prime minister. The party said Truss won the votes of around 57% of Conservative members, compared with about 43% for ex-Treasury chief Rishi Sunak.

Truss, 47, will become Britain’s third female prime minister, after Thatcher, who governed from 1979 to 1990, and Theresa May, who held office from 2016 to 2019.

Conservative Party members have embraced Truss’ vows to slash taxes and red tape and keep up Britain’s staunch support for Ukraine. Some see echoes of the Iron Lady — as Thatcher was known — in Truss’ vision of a “network of liberty” binding democracies around the world.

To critics, Truss is an inflexible ideologue whose right-wing policies won’t help Britain weather the economic turmoil set off by the pandemic, Brexit and Russia’s invasion of Ukraine.

Mark Littlewood, a libertarian commentator who has known Truss since their university days, said Britain’s new leader is less a conservative than a “radical,” who — like Thatcher — wants to “roll back the intervention of the state” in people’s lives.

“I’m expecting a lot of fireworks and a lot of controversy and a lot of action,” he said.

Born in Oxford in 1975, Mary Elizabeth Truss is the daughter of a math professor and a nurse, who took her on anti-nuclear and anti-Thatcher protests as a child, where she recalled shouting: “Maggie, Maggie, Maggie — out, out, out!”

In a 2018 speech, she said she began developing her own political views early, “arguing against my socialist parents in our left-wing household.”

The family lived in Paisley, Scotland, before moving to Leeds in northern England, where Truss attended a public high school — something that sets her apart from her many privately educated Conservative colleagues.

During the leadership campaign, Truss emphasized her relatively modest background. But she riled some former classmates and teachers when she said students at her school were “let down by low expectations, poor educational standards and a lack of opportunity.” The school’s alumni include academics, judges and several other members of Parliament.

Truss went on to Oxford University, where she studied philosophy, politics and economics — the degree of choice for many aspiring politicians — and was president of the university branch of the Liberal Democratic Party. The economically centrist Lib Dems back constitutional reform and civil liberties, and Truss was an enthusiastic member, putting up “Free the Weed” posters that called for decriminalization of marijuana and arguing in a speech for the abolition of the monarchy.

Littlewood, who was a fellow member of the Oxford Lib Dems and now heads the Institute for Economic Affairs, a free market think tank, remembers Truss as “headstrong and determined and outspoken.”

“You were never in any doubt where she stood on an issue or a person,” he said.

After Oxford, Truss joined the Conservative Party — “when it was distinctly unfashionable,” she later said.

She worked as an economist for energy company Shell and telecommunications firm Cable and Wireless, and for a right-of-center think tank while becoming involved in Conservative politics and espousing free market Thatcherite views. She served as a local councilor in London and ran unsuccessfully for Parliament twice before being elected to represent the eastern England seat of Southwest Norfolk in 2010.

She won the safely Conservative seat after a bump on the way — some local Conservatives were outraged when it was revealed she had had an affair with another MP when both were married to other people. Truss won over her critics, and her marriage survived. She and husband Hugh O’Leary, an accountant, have two teenage daughters.

She founded the Free Enterprise group of Thatcherite Tory lawmakers who produced “Britannia Unchained,” a political treatise that notoriously included the claim that British workers are “among the worst idlers in the world.”

David Laws, a former Cabinet minister who worked with Truss in government a decade ago, recalled her as energetic and “mind-bogglingly ambitious,” comparing her in his memoir to “a young Margaret Thatcher on speed.”

Truss got her first Cabinet job as food and environment secretary in 2014, making her biggest impression with a much-mocked speech in which she thundered that it was “a disgrace” that Britain imports two-thirds of its cheese.

In Britain’s 2016 referendum on whether to leave the European Union, Truss backed the losing “remain” side, though she says she was always a natural euroskeptic. Since the vote, she has won over Brexiteers with her uncompromising approach to the EU.

She became justice secretary, but she was demoted to a more junior role in the Treasury by May in 2017. When May was toppled by her repeated failure to break a political deadlock over Brexit, Truss was an early backer of Boris Johnson to replace her. When he won, Johnson made Truss trade secretary, a role in which she Instagrammed her way around the world signing post-Brexit trade deals and raising her profile.

In September 2021, she was appointed foreign secretary, Britain’s top diplomat. Her performance has drawn mixed reviews. Many praise her firm response to the invasion of Ukraine, and she secured the release of two British citizens jailed in Iran, where her predecessors had failed.

But EU leaders and officials who hoped she would bring a softer tone to Britain’s relations with the bloc have been disappointed. Amid trade wrangling, Truss introduced legislation to rip up parts of the binding U.K.-EU divorce agreement signed by both sides. The 27-nation bloc is taking legal action against Britain in return.

Truss has sometimes suggested the frequent comparisons to Thatcher are sexist, but at other times she has encouraged them. She has posed in a British Army tank in Eastern Europe, evoking an image of Thatcher during the Cold War. In a televised leadership debate, Truss sported a pussy-bow blouse just like one Thatcher used to wear.

By stressing her modest background, she is evoking comparisons to grocer’s daughter Thatcher, said Victoria Honeyman, associate professor of British politics at the University of Leeds — “the working-class girl done good.”

Truss’ own personality is hidden behind a stern public persona. Friends say she has a fun-loving side rarely glimpsed in public, and enjoys karaoke and blasting out tunes by Taylor Swift, Whitney Houston and Destiny’s Child.

Truss’ perceived loyalty to Johnson, who remains popular with many Tories, also helped her win. Many party members cited Sunak’s decision to quit Johnson’s Cabinet in July as a mark against him. Truss didn’t resign, saying she was a “loyal person” — though she had been courting party members for months at “fizz with Liz” events to build support for a potential leadership bid.

Conservatives have embraced Truss’ optimistic message of liberation through less government, which is reminiscent of Ronald Reagan’s “morning in America” boosterism.

The wider British electorate is likely to prove a harder audience to win over. Times are tough and getting tougher as inflation soars and Britain’s cost-of-living crisis worsens. Truss’ focus on stimulating the economy through tax cuts is unlikely to provide much short-term relief.

Left-of-center commentator Will Hutton, writing in The Observer newspaper, said Truss’ economic ideas were “ruinous nonsense … persistently anti-Europe, obsessed with tax cuts, buying into the faith that nameless regulations are shackling business.”

Truss doesn’t have long to persuade voters that she is on the right track. The next national election must be held in two years.

“Is Liz going to be able to say in 2024, ‘Are you richer now than you were when I became prime minister?’ Possibly,” Littlewood said. “But it’s not an obvious slam dunk.”