LONDON — British Prime Minister Keir Starmer has faced the biggest crisis of his leadership because of his decision to appoint a close ally of the late convicted sex offender Jeffrey Epstein to the plum job of U.K. ambassador to the United States.

Many warned him not to appoint Peter Mandelson, a 72-year-old grandee of the Labour Party, to the job. Starmer, who never met Epstein, accepts that Mandelson’s appointment was a mistake, and has apologized to Epstein’s victims as well as to Labour and the country as a whole.

Starmer remains in office, but questions remain as to how long he can do so.

How one appointment nearly brought the demise of the prime minister:

Under Starmer, Labour returns to power after 14 years in opposition with a landslide victory on a promise to dial down the politics, following the turmoil of the preceding Conservative years.

Starmer appoints Mandelson the U.K. ambassador to the U.S., despite knowing of his previous relationship with Epstein, who died in prison in 2019, and of his two previous resignations from Tony Blair’s government in 1998 and 2001. Mandelson, it was hoped, would be able to use his undoubted charm and networking skills to help the U.K. be spared from tariffs that the incoming Trump administration was planning.

Mandelson plays a central role in Starmer’s visit to the White House, during which U.S. President Donald Trump is invited to the U.K. for an unprecedented second state visit.

On the eve of Trump’s visit, Starmer fires Mandelson after email exchanges between him and Epstein are published, which indicate that he maintained a friendship with the disgraced financier after his 2008 conviction for sex offenses involving a minor. Starmer’s judgment in appointing Mandelson is openly questioned, and Mandelson warns there may be more embarrassing disclosures to come.

The U.S. Justice Department publishes millions of files related to Epstein.

Mandelson quits his membership in the Labour Party to avoid causing “further embarrassment” as a result of his links to Epstein. A few days later, he resigned his place in the U.K.’s revising chamber, the House of Lords.

Epstein files indicate that Mandelson shared market-sensitive information to the disgraced financier in 2009 when he was a member of then Prime Minister Gordon Brown’s government during the global financial crisis. The files also indicate that a year later, he tipped off Epstein about an imminent 500 billion-euro deal to prop up the European single currency. Payments reportedly totaling $75,000 from Epstein to accounts linked to Mandelson or his partner Reinaldo Avia da Silva are also revealed.

British police open a criminal investigation into Mandelson over alleged misconduct in public office.

Starmer agrees to release documents casting light on the decision to appoint Mandelson, and promises to introduce legislation to strip Mandelson of his honorific title of Lord Mandelson. A visibly shaken Starmer tells Parliament that Mandelson had “lied repeatedly” about his ties to Epstein. Starmer faced angry questions about his judgment, with some Labour lawmakers suggesting that he should resign.

Starmer apologizes to Epstein’s victims, saying Mandelson had portrayed Epstein as someone he barely knew. “I am sorry, sorry for what was done to you, sorry that so many people with power failed you,” Starmer said. “Sorry for having believed Mandelson’s lies and appointed him.”

Police search two properties linked to Mandelson.

Morgan McSweeney, Starmer’s chief of staff, quits, saying he takes full responsibility for advising the prime minister to appoint Mandelson. Critics say advisers advise, but leaders decide.

Anas Sarwar, leader of Scottish Labour, urges Starmer to stand down, saying “there have been too many mistakes.” Cabinet ministers rally behind the prime minister and Starmer wins the support of Labour lawmakers at a crucial behind-closed-doors meeting. “I’m not prepared to walk away from my mandate and my responsibility to my country,” he said.