The British intelligence officer who was one of Frank Hegarty's handlers and guards believes the Derry informer was sacrificed in order to protect Martin McGuinness's secret life as a spy.
Ian Hurst, using the alias Martin Ingram, was the person who outed senior IRA man Freddie Scappaticci as the British agent Stakeknife so his allegations about Martin McGuinness carry weight. Mr Guinness has strongly denied the allegations.
Mr Hegarty's family allege that Mr McGuinness lured him home from hiding in England in 1986 when he was killed by the IRA.
Mr Hurst said he was stunned when Mr McGuinness rapidly promoted Hegarty through IRA ranks despite being warned by other republicans that he was a long-standing British agent.
Mr Hurst worked in Derry for the covert military group, the Force Research Unit (FRU). "Frank was hired as an agent in the 1970s, spying on the Official IRA. His cover was blown in 1975 and he was beaten up, rather than killed by the Officials," Mr Hurst has said.
"We re-recruited him in 1982 as a low-level 'eyes-and-ears' informer to spy on the Provisional IRA. Then, myself and a colleague Brian were called in by Derry FRU boss John Tobias and told that Frank was to be instructed to get close to Martin McGuinness.
"We burst out laughing and my colleague said to Tobias, 'What have you been smoking?' Hegarty's name was mud in republican circles in Derry, nobody trusted him. We thought he hadn't a hope in hell of getting near someone as senior in the IRA, or with as much savvy, as McGuinness."
But Mr Hegarty amazingly went "from zero to hero in the Provos", Mr Hurst said."The biggest ever IRA arms shipment from Libya arrived in 1985 and McGuinness entrusted Frank with organising the dumps.
"Every senior member of the Derry Provisional IRA opposed Frank's promotion saying, 'He's a tout'. McGuinness went out on a limb for him."
Veteran Derry republican Mickey Donnelly said: "I was shocked Frank Hegarty rose through IRA ranks. Everyone knew he was an agent and that he'd a serious gambling problem."
Mr Hegarty's cover as an agent was blown when three huge IRA arms dumps were uncovered in the Republic in January 1986. He fled to England, leaving behind his partner, Dorothy Robb, and their two children – four-year-old Ryan and baby Kerri-Lee.
Mr Hurst guarded Hegarty in safe houses in the south of England: "Frank was a dishevelled working-class guy with a bit of a belly who liked a few pints, the dogs, and a bet. We hit it off because, like me, he was a gambler."
But Mr Hegarty pined for his native Derry. "He was like a homing pigeon, he just wanted back. He kept saying he could talk his way out of trouble with the IRA. He wasn't the brightest. He missed his partner Dorothy but mainly, he missed his mammy," Mr Hurst said.
Mr Hegarty rang his mother Rose every day. Mr McGuinness began visiting the house and soon started talking to Hegarty on the phone, urging him home and promising he'd be safe.
"FRU taped a conversations between Frank and McGuinness," Mr Hurst said. Mr Hurst claimed Mr McGuinness desperately needed Hegarty to come home: "For the first time suspicion was falling on him. When Frank arrived home neither FRU nor the RUC took action to save him."
The body of 45-year-old Mr Hegarty was found dumped on a border road in May 1986. He had been shot in the head. Days earlier, he'd travelled to Co Donegal for a meeting with the IRA which his family allege Mr McGuinness set up.
Mr McGuinness denies misleading the Hegartys or having any role in the murder. He has denied allegations he secretly worked for the British.