For a decade, Michael Cohen served as Mr Trump’s lawyer and backroom fixer, working, in his own words, to cover up his ex-boss’s “dirty deeds”.

But Mr Trump’s one-time henchman has transformed from arch-defender to arch nemesis as he steps up as a key witness in the former president’s Manhattan hush money trial. 

It was Cohen who facilitated, and was later jailed for, the payment to the porn star Stormy Daniels that led to Mr Trump becoming the first former US president to be indicted, and now to stand trial.

Since then, Mr Trump’s legal woes have snowballed, and Cohen has already faced off against his former boss in court, testifying against him last year in his $250 million civil fraud trial. 

Cohen, a key figure for the prosecution, told the court that he worked to boost the supposed value of assets belonging to the Trump Organization. Mr Trump was ultimately ordered to pay more than $355 million in penalties after a judge ruled he had lied about his wealth for years.

Ahead of Mr Trump’s historic first criminal indictment, Cohen stood on the steps of a New York courthouse and signalled he was primed to play a central role in prosecutors’ efforts to pursue Mr Trump.

“This is all about accountability. Donald Trump needs to be held accountable for his dirty deeds,” he told reporters, before testifying to the grand jury which ultimately voted to indict the ex-president’s fate.

The New York criminal case against Mr Trump centres on a $130,000 payment to silence Ms Daniels, real name Stephanie Clifford, over an alleged affair.

Mr Trump has always denied the claim and denounced the case as a politically motivated “witch hunt”.

Cohen pleaded guilty in 2018 to campaign finance violations over the hush money and other charges, including tax evasion and lying to Congress about a Trump business deal.

He served more than a year in jail and testified in court that Mr Trump “directed him” to commit a crime by making the hush payment with the express intention of influencing the election.

After Mr Trump’s indictment last year, Cohen said his goal in cooperating with prosecutors was to “speak truth to power”.

However, making Cohen a star witness is by no means risk-free for Alvin Bragg, the Manhattan district attorney bringing the case. 

Mr Trump’s defence team have already signalled that they will highlight the credibility issues around a disbarred lawyer with a conviction for lying during cross-examination.

During opening statements, his lawyers told the jury that Cohen “cannot be trusted” and was “obsessed” with the idea of seeing “President Trump go to prison”.

Described as a former “mega fan” of Mr Trump, 77, Cohen landed a job with the real estate mogul and reality TV star in 2006 after impressing him with his ability to anticipate his needs.

Cohen’s career route to becoming the personal lawyer for a US president was far from orthodox.

A native of Long Island, New York, Cohen attended Western Michigan University’s Cooley Law School, which has since earned a reputation as one of the worst in America.

He worked as a personal injury lawyer for a time, but built his wealth buying and selling taxi medallions in New York’s murky taxi badge industry.

Later, as the personal lawyer to one of New York’s biggest real estate magnates, he handled business deals worth considerably more.

Cohen believed his remit extended beyond official business. “I’m the guy who stops the leaks. I’m the guy who protects the president and the family. I’m the guy who would take a bullet for the president,” he told Vanity Fair during Mr Trump’s first year in office.

However, Cohen was said to be hurt that Mr Trump did not offer him a role in the White House.

Pressure mounted on Cohen when the FBI raided his home and offices and seized hundreds of items in relation to investigations into Mr Trump.

A row over who would foot the bill for his legal fees and the looming threat of a lengthy stretch in prison then paved the way for Cohen to later turn on his former boss.

He has since taken a scorched-earth approach, publishing a book titled, Revenge: How Donald Trump Weaponized the US Department of Justice Against His Critics.

In an interview with The Telegraph in 2022, Cohen hinted at what is driving his continued animus toward his former boss.

“Donald has never accepted responsibility for any of his improper actions and never will,” he said.