British authorities protected Prince Andrew from US prosecutors investigating his relationship with the financier and sex offender Jeffrey Epstein, according to a new book by a US attorney who led the investigation in New York.

Geoffrey Berman was fired as US attorney for the southern district of New York (SDNY) in June 2020. He is now the author of Holding the Line: Inside the Nation’s Preeminent US Attorney’s Office and its Battle with the Trump Justice Department, a book published on Tuesday.

Berman’s allegations of political interference in the most prestigious jurisdiction in US law have already prompted news of a Senate investigation.

His claims about obstruction in the matter of Prince Andrew and Epstein may cause consternation in a royal family dealing with the death of the Queen.

Before taking part in mourning ceremonies, Andrew had rarely been seen in public since agreeing a multi-million dollar settlement with a victim of Epstein who accused the prince of sexual assault when she was a teenager – a claim the prince vehemently denied.

Berman says SDNY prosecutors were eager to talk to Andrew about his friendship with Epstein and Ghislaine Maxwell, Epstein’s former girlfriend who in New York in June was sentenced to 20 years in prison on sex-trafficking charges.

Andrew, Berman writes, “stated publicly that he would co-operate with the investigation, and we intended to give him a chance to make good on his word”.

But though the prince “kept publicly saying that he was co-operating in the Epstein investigation”, Berman writes, that “was not true”.

Berman says he asked his team to reach out in November 2019, after Andrew gave a lengthy (and disastrous) interview to the BBC.

Two New York prosecutors “spent about two weeks just trying to find out who his lawyers were”, Berman says. “We tried calling Buckingham Palace, and they were not helpful. We tried the Department of Justice attaché and state department, no luck. When we finally got to his lawyers, they had all these questions.”

Berman says “an endless email exchange” made it “clear we were getting the run-around” from lawyers who did not want the prince to talk to the SDNY about Epstein.

“He was not going to sit down with us,” Berman writes, “despite assuring the public that he was ready, willing and able to cooperate.”

Berman says a comment he made to reporters in January 2020, that Andrew had provided “zero cooperation”, brought the prince’s lawyers back to the table. But no interview ensued.

The SDNY then tried to compel the prince to cooperate, using an M-LAT or “mutual legal assistance treaty” request via the US state department. Berman says such requests had always worked both ways before.

“But that was not what happened with Prince Andrew,” he writes. “We got absolutely nowhere. Were they protecting him? I presume someone was.”

Noting a protest from Andrew’s lawyers in June 2020 that the SDNY was seeking publicity rather than “the assistance proffered”, Berman says: “Just to be clear: there was no assistance proffered.”

He also says the SDNY was not interested in a written statement from the prince, as “that’s not how we do investigations, even for British royals”.

In keeping with his other allegations about Trump administration interference in the SDNY, Berman also says the man who fired him, then US attorney general William Barr, saw the Epstein case as a useful pawn in a political game with the British government.

Barr, Berman writes, explained “that he saw our request to talk to Andrew as sort of a chit in a dispute with the British involving a US diplomat’s wife who had accidentally killed a 19-year-old British motorcyclist in an auto accident”.

He is referring to the case of Harry Dunn, who was killed in the crash with a car driven by Anne Sacoolas, a US citizen who the Trump administration refused to extradite to face charges, citing diplomatic immunity.

“Barr told me that the public rift over Prince Andrew’s refusal to sit for an interview was useful in this other case,” Berman writes. “It inflicted PR damage, was my impression, and made it more palatable for the administration to hold firm.”

Berman says this approach “seemed questionable to me, but it did not affect our approach with Prince Andrew. I still wanted to interview him but it had nothing to do with Barr’s agenda.”