It was hardly the ending one might have scripted for a man of action. No hail of gunfire or ambushed bomb blast, nor falling victim to an assassin's blade. But as prosaic as it may sound – meeting his end while working out in a gym – the death of Old Etonian SAS officer and former mercenary Simon Mann was surely linked to a life during which hair-trigger danger had lurked in every shadow. As news of his sudden demise, aged 72, swept through London's military clubland yesterday, brother officers were wryly speculating that a man who had survived years of incarceration in not one but two hellish African jails – where other inmates died almost every day from torture, illness or starvation – should collapse while exercising. Last night Howard White, a long-time friend and business associate said: 'It's very, very sad and shocking. 'Simon was super fit. He used to go out in the mornings for a ten-mile run. But then look at the background of his life. 'I don't think five or six years in an African jail, with a hole in the ground for a toilet, did him much good. It would take a toll on anyone's health. 'He had been in the SAS – the creme de la creme. But he'd had two hip replacements, and half his body was full of metal. He said jumping out of planes with 40kgs [six stone] on his back had done for his hips and knees.' Indeed, some of his old comrades could not help wondering whether his death had something to do with his past catching up with him. How could it not? The man behind 2004's so-called Wonga Coup, with its cast of famous names that reached into the heart of the British Establishment, inevitably had enemies – many enemies. For those who liked their heroes larger than life, then twice-wed Mann fulfilled an awful lot of fantasies. Good-looking, witty and erudite while at the same time projecting an aura of menace, he was a man of secrets but also one of loyalty and courage. A soldier of fortune who made millions supplying mercenaries to protect diamond mines and oil refineries in the capitalist maelstrom of post-colonial Africa. But of all his many qualities honed on the playing fields of Eton and at Sandhurst, as well as the polish that came with membership of the elite Brigade of Guards, it was Mann's courage that was to be his most visible asset when he became involved in a plot to overthrow the tyrannical government of Equatorial Guinea. The plan was a botched disaster of epic proportions. A gun hadn't even been fired in anger when Mann and 67 fellow mercenaries, many old hands from southern Africa's apartheid era bush wars, were arrested by Zimbabwe security forces when their aircraft touched down at Harare airport to take on a consignment of arms. Mann claimed that they were on their way to protect diamond interests in the neighbouring Democratic Republic of Congo. But they were accused of being behind a coup to expel Equatorial Guinea's brutal president Teodoro Obiang Nguema. The story of the alleged coup contained more implausible characters and plot twists than any page-turning paperback thriller. There was the reputedly cannibalistic dictator who allegedly enjoyed feasting on the human remains of his foes and the lure of liquid gold – offshore oil reserves that promised to make millions for those who dared to seize them. Pictures of Mann, whose polo-playing son was best man at Prince Harry's wedding, shackled and handcuffed to his fellow mercenaries, shocked the world. But the story he scratched out on notes smuggled from his prison cell told an even more gripping yarn. It was of the people he claimed were the coup's paymasters and other figures who were said to have tacitly supported the enterprise. Along with shady tycoons, others said to be part of the murky affair included the disgraced peer Jeffrey Archer, politicians at the heart of the then New Labour government and Lady Thatcher's son, Mark, who was later arrested. In one of these notes penned during his detention, he appealed to Sir Mark to pay a 'splodge of wonga' – a large amount of money – to get him out of jail Last year, in an interview with the Daily Mail, Mann reiterated that Sir Mark was in the thick of the plot. He also claimed that over a Christmas morning breakfast with Lady Thatcher in 2003 beside the swimming pool at Mark's then home in Cape Town, the former prime minister had told him: 'I know what is going on – and you two guys have just got to get on with it.' Mann, who later removed this crucial exchange from his memoir of the failed coup at the insistence of Mrs Thatcher's lawyers, said he had no need to ask what she meant. He also maintained that this poolside message convinced him his mission had high-level approval. Sir Mark has always maintained that he was a minor investor and that he thought the money he provided was for a helicopter that would be used as an air ambulance. But after his subsequent arrest for funding an illegal coup, he agreed to a plea bargain involving admitting to lesser charges and paying a fine but escaping jail. Mann, however, a scion of the Watney Mann brewing family, spent more than five years behind bars where his resilience and his years of SAS training were to prove invaluable, not just in staying alive but also in keeping his sanity. The coup was financed by Lebanese fixer Ely Calil, nicknamed 'Smelly' by his ex-public-school co-conspirators, who later died falling down the stairs at his home in Holland Park, west London. President Obiang promised that he would eat Mann's testicles and drag his naked body through the streets should he ever get the chance. That chance came when, after four years in Harare's grim Chikurubi prison, he was extradited in secret to Equatorial Guinea, where he was incarcerated in the infamous Black Beach jail. Fears that Mann would rot away in the notorious hellhole were to prove unfounded. After only 15 months he was pardoned by the dictator he had tried to overthrow and returned to his family in England, where he was introduced to his infant son, Arthur, who had been born while he was in prison in Zimbabwe. Officially, the Equatorial Guinea regime freed Mann on compassionate grounds because of his need for medical treatment. Many observers felt the early release had been Mann's reward for his willingness to identify traitors inside the country who were in on the coup. Mann had no regrets and justified his decision because he had been abandoned himself. He also knew he would not survive even five years of the new 32-year sentence handed down to him. Simon Mann was born into a distinguished military family in 1952. His father won two Military Crosses in the Second World War and his grandfather was decorated in the Great War. Both men also captained the England cricket team, the first father-and-son pair to attain the honour. 'You have to realise that I attended lunches where everyone at the table had killed a German,' Mann once said. There was also an older cousin, Sir Lachlan Maclean, who was celebrated for his escapades in the Borneo jungle during the Malayan Emergency from 1948-1956. To augment this fascination for all things military there was the family nanny who urged him to read the derring-do stories of Biggles and Horatio Hornblower. Though his father wanted him to go into the family brewing business, he followed Sir Lachlan into the Scots Guards. When the regular Army failed to challenge him, Mann underwent the gruelling tests to join the SAS, succeeding at the first attempt and becoming a troop commander specialising in intelligence and counter-terrorism. Here he saw service in Cyprus, Germany, Norway, Canada, Central America and Northern Ireland. After leaving the military for more lucrative opportunities he went into the security business, training and providing bodyguards for oil-rich Arabs and to protect their Scottish estates from poachers. In 1990 he returned to uniform to serve on the staff of Britain's Gulf war commander Sir Peter de la Billiere. The SAS asked him to rejoin but instead he ventured with a partner into Angola's oil and gas industry, establishing a British offshoot of Executive Outcomes, the South African-based private security concern. Asked at a cocktail party what her son was now doing, his mother Margaret remarked: 'Simon always wanted his own army – and now he's got one.' Mann had three children by his first wife, Jennifer Barham, a member of the family who own the celebrated Hole Park Garden in Kent. He and Amanda were married in 1995. Also that year, he set up Sandline International, with another former Scots Guards officer, Lieutenant Colonel Tim Spicer, and it became involved in Sierra Leone's savage civil war. Sandline was alleged to have provided training and weapons to the Sierra Leone government in contravention of a UN arms embargo, helping the regime to regain control of the country's diamond fields. In the process Mann, however, became extremely rich. He bought Inchmery, a 20-acre estate on the edge of the New Forest in Hampshire, that once belonged to the Rothschilds. He also owned a private jet and a mansion in the Cape Town suburb of Constantia, where fellow residents included Earl Spencer and Mark Thatcher. There, he and his second wife, Amanda – mother of four of his seven children – became well-known figures on the Cape social scene. As well as meeting Baroness Thatcher, Mann agreed to play the part of Colonel Derek Wilford, commander of the paratrooper regiment who in 1972 fired on marchers in Londonderry, in a 2001 television reconstruction of Bloody Sunday. His next venture into the limelight was a very real drama, the Wonga Coup. The plot centred on removing President Obiang and replacing him with an exiled opposition leader. On top of a cash payment of $15million, Mann and his backers would have been granted concessions to exploit the country's vast offshore oil reserves. After his arrest in Harare, Mann was put through a mock execution by Robert Mugabe's thuggish security and threatened with being fed alive to crocodiles. To keep both mind and body active he measured the length of his cell – just seven paces – and walked the 1,560 miles from Harare to Cape Town, telling himself he would be freed when he completed the distance. When he arrived, he was still incarcerated so he set out to walk the distance back again. After publishing his memoirs, Cry Havoc, Mann struggled to find work, but two years ago he joined a green recycling company turning plastic waste into hydrogen. He attended a board meeting just hours before his death. On the domestic front, things were also not straightforward. His imprisonment took a heavy toll on his marriage and he and Amanda eventually parted. With Mann's death the curtain comes down on the era of the dashing, swashbuckling soldier of fortune...