British coup-plotter Simon Mann returned home from prison Wednesday after saying he wants the son of Britain's former Prime Minister Margaret Thatcher and others to face justice for a conspiracy to oust Equatorial Guinea's government.

Mann left the steamy island capital of the tiny oil-rich Central African nation early Wednesday after serving 15 months of a 34-year sentence. He and the four South African mercenaries who also were pardoned Tuesday had been given 24 hours to leave and can never return.

Mann did not speak to reporters upon his arrival in Britain. But his spokesman, Ian Monk, said Mann was "hugely grateful" to President Teodoro Obiang Nguema for the pardon after 5 1/2 tough years in prison and called the return the "most wonderful homecoming."

Mann testified in a trial last year that Mark Thatcher had provided $350,000, which was used to buy a small plane that was to transport Equatorial Guinea's exiled opposition leader Severo Moto from Madrid to Malabo, the capital of Equatorial Guinea.

His testimony had implicated Thatcher as chief bankroller along with Nigerian-born British citizen Eli Calil — allegations both men denied. Thatcher pleaded guilty in a South African court to unwittingly helping fund the operation. He was fined and given a suspended sentence.

Mann said after his release from prison in Malabo that he was "happy that we did not succeed in 2004."

"But as far as I'm concerned, I am very anxious that Calil, Thatcher and one or two of the others, should face justice," Mann said.

Mann said he had made statements to British investigators while he was in jail and added: "I am very happy to restate those things in court in the U.K. as a witness for the prosecution."

Scotland Yard said it was investigating whether any offenses were committed in Britain in connection with the coup plot and confirmed that a "small team" of detectives visited the country three times last year.

Mann has said he met with Thatcher and Calil in London to plot the coup — an offense under Britain's terrorism laws.

The former Spanish colony is the continent's No. 3 oil producer. The U.S. government reportedly got wind of the plot and blew the whistle, though no U.S. government official ever confirmed that. Several leading U.S. oil companies, including Exxon Mobil, Amerada Hess and ChevronTexaco, operate in Equatorial Guinea.

Mann and his co-defendants were convicted in a trial that aired a plot in which well-connected Britons and others sought to install Moto. The coup unraveled before it even began, when Mann and a planeload of other mercenaries were arrested in Zimbabwe where they were to buy assault rifles, grenades and anti-tank rockets.

Supreme Court Chief Justice Jose Obono Olo said Tuesday that the president had granted the five men full pardons on humanitarian grounds.

South Africa's role in the men's release remained unclear. The pardon came the day before South African President Jacob Zuma arrived on an official visit, Zuma's government said it had not sought the men's release.

However, the leader among the South African mercenaries, Nick du Toit, credited Zuma for their freedom.

"We were told that Zuma and his government were involved in the negotiations for our release," du Toit told The Star newspaper of Johannesburg.

Equatorial Guinea's Information Minister Jeronimo Osa Osa Ekoro told the AP that the presidential pardon was aimed at "extending a hand of friendship and democracy to South Africa, with which we have good relations, and was a demonstration of humanity to forgive these men who really tried to damage our country."

Mann was born into a life of wealth and privilege, a former officer in Britain's elite SAS who was educated at Eton, a prestigious British private school whose alumni include Princes William and Harry. Mann is the son of former England cricket captain George Mann and heir to the Watley Ale brewing fortune.

Simon Mann later helped found two South African private security companies — Executive Outcomes and Sand-line — that were involved in some of Africa's bloodiest civil wars. Executive Outcomes made millions guarding Angolan oil installations and helping rout rebels in Sierra Leone with brutal actions.