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 since becoming mired in legal trouble of his own, Mr Trump’s one-time henchman has transformed from archdefender to archnemesis.

It was Cohen who facilitated, and was later jailed for, the hush money payment that led to Mr Trump becoming the first former US president to be indicted.

Since then, Mr Trump’s legal woes have snowballed, and Cohen is set to turn on the former president once again by testifying against him in his $250 million fraud trial brought by New York Attorney General Letitia James.

‘Dirty deeds’

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

“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 will decide the ex-president’s fate.

The New York criminal case against Mr Trump centres on a $130,000 payment to silence Stormy Daniels, a porn star, over an alleged affair.