Meet the little-known accountant who could be about to bring down Donald Trump

The list of Donald Trump associates who have attempted to bring down the former president is as long as it is varied: from his lawyer, to his closest advisor, his ex-wife and his alleged lover. But like many powerful figures before him, it may well be his accountant that would be his undergoing.

Allen Weisselberg, the little-known 73-year-old chief financial officer for the Trump Organisation, has worked for the Trump family as far back as the early 1970s under Donald’s father Fred. Some say he is closer to Mr Trump than he is to his own children. As one former employee put it, “he knows where the bodies are buried".

In recent weeks New York prosecutors investigating Mr Trump’s tax affairs have been turning the screws on Mr Weisselberg in the hope of flipping him to testify against his boss.

Cyrus Vance, the Manhattan District Attorney, is looking into everything from hush-money payments paid to women on Mr Trump's behalf, to property valuations and employee compensation.

Speculation is mounting that his office may be able to turn Mr Weisselberg, who has not been accused of any wrongdoing, as it pulls together a grand jury to decide whether to indict.

Mr Trump has repeatedly denied the allegations and dismissed the investigation as politically motivated. Mr Weisselberg has not commented on any of the legal issues.

"My gut tells me that this will rise or fall on one person: Alan Weisselberg,” said Elie Honig, a former New York federal and state prosecutor. “If prosecutors can flip Weisselberg - and this grand jury can charge anybody - he can tell them what Donald Trump knew and authorised."

Without an insider it can often be difficult to put all the pieces in a white-collar case together.

The Trump Organisation may be a sprawling business enterprise with over 350 employees, but at the top there are just three loyal lieutenants: Mr Trump’s sons, Donald Jnr and Eric, and Mr Weisselberg.

Having spent half a century managing the family’s accounts, Mr Weisselberg has played significant roles in businesses ranging from Miss Universe, to Trump Towers, to the president’s casinos.

The pressure was raised on Mr Weisselberg last week after his own tax returns were probed, with investigators hoping to gain leverage that could convince him to cooperate.

They have even subpoenaed financial records of the private school attended by his grandchildren, believing tuition payments were part of Mr Weisselberg’s compensation package at the Trump Organisation. Prosecutors say it could amount to tax evasion, which is a criminal offence.

The testimony of the unassuming accountant has brought about the downfall of many high-profile figures throughout history. It was Frank Wilson who helped put away notorious mob boss Al Capone in the 1930s. More recently, David Friehling’s evidence proved essential in prosecuting financier Bernie Madoff over his multi-billion dollar Ponzi scheme.

To add to Mr Weisselberg's woes, former associates of Mr Trump's who have already turned supergrass are attempting to implicate the CFO in Mr Trump's underhand dealings.

Michael Cohen, Mr Trump's personal lawyer at the start of his presidency, has accused Mr Weisselberg of arranging for the Trump Organisation to pay him $35,000 (£22,000) a month, to reimburse him for hush money Mr Trump had asked him to pay adult film actress Stormy Daniels to keep quiet about an alleged affair.

Mr Weisselberg was subpoenaed to testify before a federal grand jury regarding the Cohen investigation but was granted limited witness immunity for his testimony and faced no charges of his own.

However, Mr Weisselberg’s federal immunity does not extend to state investigations.

The threat of criminal investigations into his taxes was a spectre that haunted Mr Trump throughout much of his presidency, providing an added impetus to secure a second term which would have shielded him from prosecution.

In his 20s, Mr Trump built his empire on publicity and gained fame, while Mr Weisselberg, who is one year younger than the former president, worked behind the scenes to help create the jumble of roughly 500 companies that make up the Trump empire into what it is today.

Mr Trump’s personal and professional lives were often blurred. The Trump Organisation’s boardroom provided the set for Mr Trump’s TV series The Apprentice. Mr Weisselberg himself appeared as a judge on the seventh episode of the second season.

The Weisselberg and Trump families too have become intertwined over the decades. Alan’s son Jack is an executive at Ladder Capital, which has acted as a lender to the Trump Organisation. Another son, Barry, has managed the Trump Organisation's Central Park ice rinks.

Jennifer Weisselberg, Mr Weisselberg’s former daughter-in-law, once said of him: "He has more feelings and adoration for Donald than for his wife. For Donald, it's a business. But for Allen, it's a love affair.”

The former ballet dancer, who has two children with Barry, has begun speaking out publicly on the investigation, predicting this week that her father-in-law may well cooperate to protect the family.

Ms Weisselberg has said several members received free use of Trump Organisation apartments and alleged that her ex-husband laundered money through the ice rink operations.

Barry Weisselberg did not reply to request for comment, nor did the Trump Organisation.

Ms Weisselberg, who claimed this week she had been evicted from her Manhattan apartment for cooperating with authorities, told NBC News that Allen Weisselberg discusses 'everything' with Mr Trump about the company’s financial workings. “And Donald trusts him to continue the legacy the way his father set things up,” she said.

"I contacted Allen numerous times last year to try and discuss this privately, with dignity, gracefully, within the family," she said. "He wasn't interested."