Simon Mann, the Old Etonian mercenary who plotted to seize a tiny West African state, will arrive back in Britain today to a five-year-old son he has never seen, questioning by Scotland Yard and a welter of lucrative offers for his astounding story.

The former SAS officer was released yesterday by Teodoro Obiang Nguema, President of the corrupt but fabulously rich oil state of Equatorial Guinea, after Mann had served only 15 months of a 34-year jail sentence for conspiring to overthrow him.

He was informed of his imminent release on Saturday by Jose Ole Obono, the chief prosecutor in the trial. “His eyes filled with tears,” Mr Obono said.

Mann’s brother, Edward, and sister, Sarah, flew to Malabo, Equatorial Guinea’s capital, for an emotional reunion after he left Malabo’s infamous Black Beach prison yesterday afternoon. They were spending last night in a luxury hotel owned by the Minister of Security. Mann, who was given 24 hours to leave the country, is expected to fly home on a private plane paid for by unnamed “friends”.

The Government in Malabo said that Mr Obiang had pardoned Mann, 57, purely on humanitarian grounds, adding that he needed “regular medical treatment near his family”. Mann has had two hernia operations since he was sentenced in July last year, though various sources told The Times that he was now in good health.

There was speculation, however, that his early release was a reward for having testified that foreign governments and a bevy of prominent businessmen, including Sir Mark Thatcher, were part of the plot to seize Equatorial Guinea’s oil riches. Augustin Nze, the state’s Ambassador in London, insisted: “That’s nonsense ... There was no deal.”

The timing of Mann’s release may also have been dictated by the expected arrival in Malabo today of the South African President, Jacob Zuma. Four of Mann’s fellow mercenaries, all South African, were also freed.

Mann’s family, who live on a 20-acre estate near the New Forest, issued a statement that they were “overjoyed at the prospect of finally welcoming Simon home after five and a half long years”, and added: “Everyone is profoundly grateful to the President and Government of Equatorial Guinea.”

The Foreign and Commonwealth Office denied there had been any negotiations between Britain and Equatorial Guinea. Greg Wales, a London businessman and fellow plotter, said that he had held secret talks with the Equatoguinean Embassy in Mayfair to secure Mann’s freedom, but Mr Nze said the meetings played no part in the President’s decision and there were no conditions attached to Mann’s release.

Sources told The Times that publishers and newspapers were already bidding for Mann’s story.Mann was born into a life of wealth and privilege. He went to Sandhurst and joined first the Scots Guards and, later, the SAS. He then co-founded a company that sent mercenaries to fight rebels in Angola and Sierra Leone and made enough money to buy Inchmery, a Hampshire estate that had belonged to the Rothschild family, in 1997. But his hunger for adventure could not be satisfied by mixing with the great and good. Soon he and his third wife, Amanda, moved to Cape Town, where he fell in with the likes of Sir Mark Thatcher and hatched a plot of stunning audacity and startling ineptitude.

The idea was to seize control of Equatorial Guinea, Africa’s thirdbiggest oil producer, and replace Mr Obiang with Severo Moto, an exiled opposition leader living in Madrid. It would be nice to think that Mann’s motives were altruistic, Mr Obiang being the head of a venal regime where the favoured few enjoy fabulous wealth while most of the 700,000 population live in squalor. What he was after was a “splodge of wonga”, allegedly $15 million, for services rendered. Mercenaries were recruited and planes bought, but the plot was an open secret. On March 7, 2004, Mann and more than 60 “dogs of war” were arrested when their Boeing landed in Harare, the Zimbabwean capital, to pick up arms en route from South Africa to Equatorial Guinea.

Mann spent nearly four years in Chikurubi prison in Harare. On his release he was spirited away to Equatorial Guinea.

His trial opened in Malabo in June last year. Foreign journalists were, for once, admitted to the ultra-secretive state. The entire event seemed designed to burnish the image of a rotten regime, to suggest that it was the victim of international skulduggery, and Mann turned in a virtuoso performance despite being quite unable to follow the Spanish proceedings.

His script might have been written by the regime. He described Sir Mark as part of the plot’s “management” team, not the “unwitting” financier that Sir Mark has claimed.

Mann claimed that Ely Calil was the “boss” — a charge Mr Calil has always denied. He said that the Spanish and South African governments sanctioned the coup attempt, and that the Pentagon, CIA and US oil companies that invest so heavily in Equatorial Guinea gave their tacit consent.

Mann’s 34-year-sentence came as a shock. Not even the prosecution had demanded that. But one Equatoguinean lawyer told The Times that the trial was a charade, and that Mann “will be pardoned within a year, two at most”. And so it has turned out.

Mann has been spared the hardships that befall most inmates of Black Beach, a prison renowned for torture, unexplained deaths and starvation. He had his own cell, exercise machine and books and was allowed regular calls home. He often had lunch with Manuel Nguema Mba, the Security Minister, who would bring food and wine from his hotel, the Paraiso, where Mann spent last night.

When he arrives home, he will be reunited with his wife and seven children, the youngest of whom was still in his mother’s womb when he flew off to Zimbabwe on his ill-fated escapade. That is not the end of the “Wonga Coup” saga, however. Scotland Yard monitored the trial, and when it was over it began an investigation to determine whether any offence had been committed in Britain. Police officers visited Malabo three times, but have yet to question Mann. Sources close to the family fully expect them to do so now. Mr Obono, the chief prosecutor who is now president of Equatorial Guinea’s Supreme Court, said that his Goverment still regarded Sir Mark and Mr Calil as wanted men.

Despite Mann’s damning testimony, Sir Mark issued a statement saying he was “delighted that Simon will be reunited with his family at last”. Mr Calil, likewise, said that he was “thrilled”.

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