The mercenary accused of plotting to topple the President of Equatorial Guinea is expected to name the backers of the failed coup, after attempts in the High Court to block a television interview failed.

Channel 4 is preparing to broadcast footage of Simon Mann speaking from the Black Beach prison in Equatorial Guinea, in which he is expected to talk about the events leading up to the botched coup before his trial next week.

Attempts to block the broadcast were reportedly made by a lawyer acting on behalf of Mr Mann’s wife, Amanda, even though the Government of Equatorial Guinea has suggested the interview could help to earn Mr Mann’s release. It is expected to be shown this week, although lawyers believe that Eli Calil, a Lebanese financier and oil trader, may also seek an injunction.

Mr Mann allegedly accuses Mr Calil, who is worth £100 million, of backing the coup, according to The Mail on Sunday yesterday. Mr Calil has denied involvement. Andrew Kerman, the lawyer instructed by Mrs Mann, is a close associate of Mr Calil, according to reports. The role of Sir Mark Thatcher, the son of the former Prime Minister, is also believed to come up. He was fined £265,000 and given a suspended jail sentence in South Africa for helping to finance the alleged coup. He was spared prison after a plea bargain affirmed he had helped unwittingly.

The interview could put pressure on Scotland Yard to revive its investigation, dropped so police could shift resources to the bombings in London in July 2005.

Mr Mann has denied plotting a coup, saying he was providing security for the diamond industry in the Democratic Republic of Congo. He was arrested in Zimbabwe in March 2004 when he and 68 South African and Angolan mercenaries arrived in Harare, allegedly en route to Equatorial Guinea. The aircraft was to be loaded with arms worth £100,000.

Mr Mann was convicted of breaching Zimbabwe’s immigration laws and had served almost four years in jail before being deported to Guinea.

His wife has said he was effectively “kidnapped” and repeated claims that President Nguema threatened to “sodomise” her husband and skin him alive. But pictures show Mr Mann appearing fit and healthy.

Confusion surrounds the reasons for the injunction. It was granted, but on Friday the legal team “shifted its position” after Mr Mann’s sister Sarah and brother Edward returned from visiting him in jail.

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