The British man being put forward by Donald Trump’s campaign team as a witness to his innocence in a sexual assault allegation has a record of involvement in political scandal and unproved allegations, financial mismanagement and taking money from a newspaper to expose a Tory MP’s sex scandal.

Anthony Gilberthorpe, a 54-year-old former Tory activist, antiques dealer and Big Issue seller from Gloucestershire, claims his “photographic memory” enabled him to recognise Jessica Leeds when he saw her last week on a US news report talking about how Trump had assaulted her on a flight between Dallas and New York in 1979.

Gilberthorpe contacted Trump aides to say he had been on the flight sitting across from Trump and Leeds and saw “nothing untoward”. Although he thought the flight had been 1980 or 1981, Gilberthorpe told the New York Post on Saturday that “it was she that was the one being flirtatious” and that she had told him she intended “to marry” Trump.

They got on so well that Trump gave the cufflinks he was wearing to Gilberthorpe, then a teenager, at the end of the flight. Neither the New York Post nor the Trump campaign would say if he has been paid for his intervention.

Jessica Leeds, one of two women who told the New York Times that Donald Trump molested her. Photograph: Julie Jacobson/AP

In 2014, Gilberthorpe told the Daily Mirror he went “trawling” the streets to procure underage boys for Tory MPs for sex and drugs parties – including some in Margaret Thatcher’s cabinet. He claimed to have recruited rent boys, the “youngest and prettiest”, for parties at conferences in Blackpool in 1983 and to have attended parties in Brighton in 1981 and 1984. He named high-ranking politicians, all of whom were by then dead, as being part of the paedophile parties when he spoke to the Mirror, calling himself a “whistleblower”.

Gilberthorpe was still a teenager when he inherited £250,000 after the death of an elderly man with whom he had become friends. “That was what funded his jet-set life – or that was what he liked to call it,” said a former local news reporter in Gloucestershire where Gilberthorpe began what he hoped would be a stellar political career by becoming a county councillor. “He firstly bought a care home and that didn’t work out, then it was antiques. I was bit shocked to see him in the Big Issue magazine a few years ago however, complaining about how all his friends deserted him when he became bankrupt.

“He was forever dropping into our office in Gloucester and giving out little titbits about himself. Knowing the man I knew back then, someone who sought publicity constantly, this latest outing for him is par for the course for Gilberthorpe,” he said.

In 1987 the reporter took a call from Gilberthorpe. “He said he was resigning as a councillor because the Express was about to out him as gay and claim he had been travelling back and forth to New York for treatment for Aids. He told me he was calling from New York. Turned out he wasn’t. I asked if he did have Aids but he didn’t answer.”

Gilberthorpe, although admitting in court later that he had told lies, including fabricating an engagement to an American heiress, sued several newspapers who printed the allegations he was promiscuous and had Aids. He won his libel case in 1988 but, in an unusual legal move, it was overturned by court of appeal judges shortly afterwards, leaving him without the payout he anticipated.

The key witness for his claim in the libel trial was Tory politician Piers Merchant. In 1997, Merchant, then MP for Beckenham, asked to borrow Gilberthorpe’s York flat for a meeting with his mistress, 18-year-old Anna Cox, unaware that Gilberthorpe had accepted an estimated £25,000 from the Sunday Mirror to allow the flat to be filled with recording and video equipment. The exposure of the married MP’s affair led to the end of his career and the memorable headline that haunted John Major’s government: “Sleaze Merchant”.