Our father, the mercenary

THE GARAGE smelled of death. Flies' eggs nestled amid piles of clothes, a BB gun was propped against one wall, and in the corner a small cooking stove showed signs of use. The ground was covered in boxes of papers – faxes, manuscripts, printed-out e-mails, photographs – each box heavier than the last. "But," asked 27-year-old Paul Sessarego, looking around in confusion at the tiny, cramped room where his father had died, "where was he sleeping?"

For Paul and his sister, Claire, 30, this trip to a rented garage in a rundown part of Antwerp was the closest they had come to their father, Philip Sessarego, in 15 years. Yet when the call came in November of last year to tell them that the rotting corpse of a British man, whom they suspected to be Sessarego, had been found in a Belgian lock-up, they were not entirely surprised: after all, it was not the first time they had been told their father was dead.

Tonight's First Cut: My Father The Mercenary looks at the extraordinary story of Sessarego, a soldier for hire who was involved in a failed coup in the Maldives and also trained Mujahideen in Afghanistan, before faking his own death in 1993 on the battlefield in Croatia. He reinvented himself as Tom Carew, an ex-SAS soldier and author of Jihad!, a book about the West's "secret war in Afghanistan", only to be exposed by a Newsnight investigation in 2001 as a fraud who had twice failed SAS selection. Meanwhile, he left a trail of emotional destruction across Europe, abandoning at least two families and refusing to acknowledge his own children.

"No matter what he achieved in life, this notion of being in the SAS remained the pinnacle of everything he wanted to do," says documentary-maker James Ross, who followed Sessarego's two children as they travelled to Antwerp earlier this year to collect their father's ashes and unravel the mystery of his final years.

"In the end, he sacrificed everything for it. He sacrificed his family for that fantasy."

Philip Anthony Sessarego was born in 1953 in Dorset. He did not shine at school and his early life was unhappy. "He had a very hard childhood," says Ross. "There's speculation now over who his father really was. His mother was a hard woman and he didn't have a good relationship with her."

Spending his summers on a farm owned by an uncle in Hereford, the local town for Britain's élite SAS regiment, Sessarego came to idolise the dashing military men he occasionally saw on the streets. "They became his heroes," says Ross. "They became the escape from a childhood that he wasn't really enjoying."

After leaving school with few qualifications, he joined the army and served in the Royal Artillery. In 1973 he tried out for 22 SAS, but failed its notoriously stringent entrance test – part of which involves marching 40 miles across the Brecon Beacons in less than 24 hours – owing, it is thought, to a knee problem.

Failure, however, only served to increase Sessarego's SAS obsession. He moved his wife, a Scot named Diane, whom he had married aged 19, and their two young children, Paul and Claire, to Hereford, where he ran several miles every day to improve his fitness. He tried the SAS entrance test again, failed by nine out of ten regular army men, and lost out once more. He was devastated, even though the regiment kept him on as a member of the "goon troop", a group of narrowly failed soldiers who were retained at the SAS's HQ to take part in training exercises. But it wasn't enough. In 1975 he left the army. He was 23 years old.

"He was never a badged member of the SAS, but he had the same thing that drives all of us to get into the SAS, and that's ego," says Clive Fairweather, a former deputy commander of the SAS. "In life, you will always find men who would like to be in something secret, something really dramatic, like the SAS. For the guys who pass the entrance test, most of those fantasies about SAS life eventually erode when they see the harsh realities of the regiment. But for those who fail, many never get over it. They start to create a web of fantasy around themselves and they go to extraordinary lengths. It goes on all the time."

For Sessarego, his departure from the army marked the start of his fantasy life. Over the next 18 years he found work as a mercenary in various hot spots around the world, becoming involved in murky dealings in countries from the Dominican Republic to Afghanistan, where he spent time – or so he later claimed – training the Mujahideen. Wherever he was, he usually claimed to be an ex-member of the SAS.

Adrian Weale, a former military intelligence officer who ghostwrote Jihad! and spent many hours with Sessarego in the late 1990s – who was by then living in Belgium and going by the alias Tom Carew – says it was difficult to separate fact from fiction.

"A good deal of it was true, but the $64,000 question is how much," he says. "When I eventually found out what his real name was, I did some checking. He certainly pops up in newspaper stories from the time as being involved in the Maldives coup and working as an Afghan mercenary, so that side of it had a strong element of truth. But, I think, mixed into that was an element of fantasy, and it's very difficult to know where the line was between the two."

Fairweather, too, believes that Sessarego worked in Afghanistan in some capacity. "I read enough to convince myself he was there," he says. Whatever the truth, in 1993 Sessarego managed to annoy enough people while operating in Croatia, possibly with Operation Clover, a US intelligence-sponsored op that provided covert support to the Croatian and Bosnia-Herzigovinan governments during the war with Serbia, that he faked his own death. By this time he had been separated from Claire and Paul's mother for several years. The family believed their father was dead, killed in a bomb explosion.

However, on 10 September, 2001, Jihad! was published in paperback and, following the cataclysmic events of the following day, "Tom Carew" was suddenly in demand by TV channels as a military pundit. Sessarego's children were shocked to discover that he was still alive, and eking out rather a nice living as Carew, ex-SAS soldier and author of Jihad!. Weale says he rarely mentioned his children when working on the book.

"He did talk about his family in Hereford occasionally," says Weale. "But I had no idea how many families he had. He seemed to have this fairly extensive network of children around Britain and Europe." Weale thinks Sessarego had the ability to close the door on emotional elements in his past. "I never saw any regret there. He didn't seem to understand children at all. He didn't have a clue what kids wanted in life."

One of the most poignant moments in the documentary shows Claire and Paul raking through boxes of their father's papers and manuscripts, desperately trying to find some small scrap of evidence that they were still in his thoughts. Instead, they find a picture of an unknown woman with a small child. Their reaction, when they realise they could be looking at a picture of their half-sibling, is heartbreaking.

In November 2001, Sessarego's life came crashing down. An irked military source is believed to have tipped off the BBC's Newsnight team that the successful author was not all he seemed. A number of SAS members spoke to the programme, telling them that "Tom Carew" was a fiction and had never been a member of the regiment. After weeks of tense negotiating, during which Sessarego claimed to a Newsnight reporter that he had a security team of 11 Albanians that "like to shoot first and ask questions later", he finally agreed to an interview. Confronted with the evidence, he realised the jig was up. He walked out, demanding to see evidence in writing and pushing a camera out of his face. Then, he simply vanished from public view.

"Immediately after the interview he phoned me and he was really furious, making death threats and all sorts of things," says Weale. "After that he went quiet for a few weeks. Then he sent me an e-mail, which wasn't quite an apology but an explanation of why he hadn't gone into the SAS. He did, in the end, admit to me that he hadn't been in the regiment. But he was still very upset, because the interview had blown away his fantasy life."

For the next seven years Weale remained in Belgium, working on the docks in Antwerp and still living out the fantasy SAS life. Before moving into the garage, he lived rough in the woods, despite having a well-paid job that could have easily paid for a furnished flat. There were other girlfriends ("He told me once he was living with a 19-year-old lingerie model," says Weale) and possibly other children.

His death last summer from – according to the post-mortem examination – carbon monoxide poisoning went unnoticed until November, when the man from whom he rented the garage broke in to demand several months' worth of unpaid rent. "When I heard he was dead, it struck me as not impossible that somebody might have had him killed," says Weale. "I really don't know."

For his children, there remain a number of doubts – over his life as well as his death.

"Claire's never going to know the full picture," says Ross. "At what point do you know enough to be able to walk away from it? She still jokes that he's going to turn up again. A part of her still believes he might walk through the door one day."

• First Cut: My Father The Mercenary, Channel 4, 7:35pm tonight