The curious case of Simon Mann

So Simon Mann, international man of mystery, the very model of a modern day mercenary, is free. Sentenced last year, after a show trial, to 34 years in jail (plus a few million dollars in fines) to be served in the notorious Black Beach prison in Malabo, Equatorial Guinea, he should be back in London within a day or two.

His crime – to which he confessed in great detail, though under harsh conditions (he reasonably feared that he might be tortured) – was to plot the overthrow of the government of Teodoro Obiang Nguema Mbasogo in 2004. Having recruited dozens of hired guns, veterans from wars in Angola, Iraq and elsewhere, he arranged for his teams to fly at night to Equatorial Guinea, in early March 2004, to carry out a daring putsch worthy of an airport thriller. He was foiled en route, however, in Harare, Zimbabwe, when Robert Mugabe's officials – who had been in the process of selling weapons to the mercenaries – instead arrested the plotters at the airport.

In a letter to his wife, Amanda, from prison in Zimbabwe, Mann described how he had dreamed of seeing the "Welcome to Heathrow" sign. Since his arrest, five years ago, he was moved from one wretched jail in Harare to another in Malabo. He claimed that he was violently abducted and flown in secrecy, and illegally, via a third country to Equatorial Guinea – the sort of fate, "extraordinary rendition", more usually associated with terrorist suspects. A clutch of other foreign prisoners who were also convicted of being part of the plot are also to be freed. But it is unclear whether hapless local prisoners, accused of similar crimes but without the benefit of foreign attention, will be freed.

I don't think there has been a grand deal between Britain and Equatorial Guinea to secure Mann's freedom. Mann himself had been a compliant prisoner – opening his diaries and other documents to investigators, accusing others of being part of the scheme and talking openly and in detail about the plot. The government in Malabo wanted British authorities to prosecute others, in return for Mann's freedom, but I doubt that Scotland Yard was in a position to do such a deal, even if (which is unlikely) political authorities thought getting Mann's release was a priority. Certainly the government in Equatorial Guinea didn't seek a big bribe to free Mann: as one of Africa's main producers of oil, the country is awash with cash.

Mann can expect to return to a flurry of questions. Most generally, will he stand by his repeated confessions made in courts in Zimbabwe and Equatorial Guinea, and in detail to visiting teams of television journalists, in which he owned up to the plot ("tiger-hunting" he called it) and apologised profusely? He offered at one point to tattoo the word "sorry" on his forehead. And will he repeat claims that prominent individuals were involved? Most notably will he say that Mark Thatcher, son of the former prime minister Baroness Thatcher, was not an unwitting investor in the plot but also an "intimate" tactician? When I interviewed Thatcher for my book The Wonga Coup he admitted he had provided money to Mann, but that he thought the cash was to fund an air ambulance. Mann, however, suggested that Thatcher discussed minute details of the plot with others involved. Mann also accused a Lebanese businessman, Ely Calil, of being "The Cardinal", the mastermind of the plot. Will Calil, an associate of Lord Mandelson, again be accused by the former SAS officer?

It would be simplistic to see Mann as a proxy for western interests as a whole, but some will reckon that the only thing outsiders care about is getting control of Africa's natural resources. Mann may say he had more noble ambitions – that he had great pity for the ordinary people of Equatorial Guinea who were suffering repression – but his interests in fact seem largely personal. He wanted an adventure, the chance to act out a thriller with him as the hero. He also wanted that big "splodge of wonga". Perhaps he can get a job playing the lead role in The Wonga Coup: The Movie. His first ambition, however, is presumably to see his youngest son, Arthur, born several months after his father's adventure fell apart spectacularly.

Adam Roberts, the news editor of Economist.com