A Co Antrim private detective has told of his guilt over rumbling one of Hollywood's biggest icons for having an affair that ended her A-list marriage.
He's also lifted the lid on how he did time with IRA chiefs, helped nail Margaret Thatcher's son for his part in one of the world's most infamous coups and was banged up at a "hellhole" Argentina jail while hunting missing kids.
Ian Withers (80) was tasked with tracking America's 1970s golden girl Farrah Fawcett at the peak of her Charlie's Angels fame.
The blonde was said to be having a fling with volatile actor Ryan O'Neal behind the back of her Six Million Dollar Man star husband Lee Majors.
Ian was paid by US gossip magazine the National Enquirer to get proof. It led to an extraordinary meeting over drinks with Farrah in London who handed him her itinerary while she was in England so he could track her round the clock.
Revealing details of the case in his upcoming memoir Private Eye, Secret Spy: My Life As Britain's Most Controversial PI, ex-cop Ian said: "Was one of Charlie's Angels doing the dirty on the Six Million Dollar Man? It's a question which caught the attention of many millions of people in the Seventies. And I was asked to answer it."
Ian used a motorcyclist and car team to start 24/7 surveillance on Farrah while she was in London.
He and his outfit watched as she was shuttled from an apartment on Wilton Row, Belgravia, to Shepperton Studios - where she was filming a sci-fi flick called Saturn 3 alongside Kirk Douglas and Harvey Keitel.
But Ian underestimated her security detail who soon clocked him and his team.
They got paranoid he was part of a kidnap gang as Farrah had recently been the victim of a failed attempt to snatch her while she was filming in Mexico.
One Friday afternoon while watching Farrah's flat, Ian said one of her "goons" tapped on the window of his car - and when he refused to open it, snapped off the antenna of his car radio.
The hulking bodyguard returned minutes later and told the PI: "'The lady wonders if you would like to have a drink with her - she wants to ask what you're doing'."
Ian arranged to meet her at a pub opposite her apartment.
"A few moments later and one of Charlie's very beautiful angels walked out wearing her very skimpy white outfit and a long overcoat on top," he recalled.
"I was as professional as I could be, of course, but I do accept my jaw may have dropped open as those endless legs strode across the road in front of me."
Over a fruit juice for Farrah and tonic water for Ian, she used her "silky, soft Texan accent" to explain she was "kinda nervous" at being watched after her brush with kidnapping in Mexico.
After he admitted he was from the Press, Ian said Farrah "reached into the inside pocket of her coat and handed me three sheets of paper - they detailed her movements over the following four days".
The itinerary allowed Ian to capture Farrah cosying up to Love Story star and legendary womaniser Ryan O'Neal at a Chinese restaurant in Mayfair.
Farrah divorced Lee Majors and she and Ryan, now 79, went on to become the Angelina Jolie and Brad Pitt of their day.
They stayed together until Farrah's agonising death aged 62 from cancer that spread to her liver.
Ian confessed: "I can't get away from the guilt that comes with it. She was striking and gracious and, no doubt, was already resolved to closing down her relationship with her husband at the time.
"Yet the distress that came to her on that night in London was as a result of my work."
Far less glamorous were the months Ian was banged up at HMP Brixton for 'conspiracy to commit a public mischief' due to a technicality over the way he accessed people's private information for clients.
Weeks into Ian's sentence, IRA bomber Gerry Kelly was locked in the prison's A-wing with the other members of a republican terror cell that killed one and injured 200 in the 1973 Old Bailey blast.
Military-trained dad-of-four Ian - whose late wife Phyl had seven relatives in the RUC - said about the bomber turned Sinn Fein politician: "Our exchanges were pleasant enough but, as an ex-soldier, it was hard to avoid the idea he was part of an organisation which murdered troops whenever it could."
Ian's book tells how he was also jailed in a "cesspit hell on earth" Argentina jail for a week while searching for two missing children.
Authorities had mistaken him for a CIA spy out to topple the country's brutal dictatorship and bolted him in a nightmarish cell where giant cockroaches scuttled over his body while the screams of other inmates being tortured echoed in the darkness.
Ian - who ran a global PI agency for 60 years - made headlines three years ago when he was arrested but bailed without charge over the unsolved 1985 shotgun assassination of exiled Seychelles dissident Gerard Hoarau.
As we revealed last week, he is still fuming the Met Police maintain he's still a suspect.
Ian's gripping memoir also details how records of phone calls he collected helped in the conviction of the late British Prime Minister Margaret Thatcher's son.
Mark Thatcher (67) was handed a four-year suspended sentence and fined £226,000 for his part in a failed coup in Equatorial Guinea.
Private Eye, Secret Spy: My Life As Britain's Most Controversial PI is due out May 2021. See http://www.idwitherspi.com for more information about Ian and the book.