A royal aide boasts about his fling with an MP in a tape at the centre of the sex-and-drugs blackmail plot concerning a member of the Royal Family, a lawyer claimed yesterday.

The assistant to a minor relative of the Queen also claims that the true medical cause of death of a member of the Royal Family may have been concealed from the public.

Police investigating the alleged plot have seized several mobile phones belonging to Ian Strachan, 30, a socialite, and are expected to check the handsets for stored video files, records of texts and calls. Prosecutors will object to Mr Strachan, who is being held at Belmarsh high-security prison, being given bail when another court hearing is held behind closed doors tomorrow, his lawyer said. Sean McGuigan, 40, from Battersea, was also arrested.

Transcripts being studied by lawyers allegedly show a royal aide specifically admitting to a “tryst” with an unidentified MP. Scotland Yard was called in to investigate the alleged £50,000 plot when staff of the Royal Family member became concerned about the activities of certain individuals. An undercover detective from the Metropolitan Police kidnap and blackmail unit, along with a representative of the Royal Family member, went to the Hilton Hotel in Park Lane, London, and met the alleged blackmailers on September 11. It appears that some video material, involving a royal aide talking freely about his claims to know society secrets, was shown.

Mr Strachan, a party-loving property developer from Aberdeen, who has Icelandic origins, is being defended by Giovanni di Stefano, a Rome-based lawyer whose past clients included Saddam Hussain and Harold Shipman. Mr di Stefano said that his client never telephoned any member of the Royal Family, aides or assistants to make a blackmail claim and that the Crown accepted this. The lawyer said that it was suggested at the Hilton to Mr Strachan that if £50,000 were paid to him, the videos would never be disclosed to a wider public. Mr Strachan is said to have simply agreed with the suggestion put to him. Far from being a blackmailer, he had failed to accept any cash from members of the press who had shown interest in the tapes.

“This is about keeping these people in custody,” Mr di Stefano said. He said that the authorities feared what might happen if the suspects were freed to tell their story. A judge took the unusual step of holding the preliminary hearing at City of Westminster Magistrates’ Court in camera, with press and public excluded, on September 13. An order was issued forbidding publication of any details that could identify witnesses or alleged victims. Even if the criminal case collapses, legal experts predict that the ban on identifying the alleged blackmail victim will remain in place.

“They could have obtained a whole heap of money from a number of newspapers that had offered,” Mr di Stefano said. “But this was more of an attempt of showing the member of the Royal Family that the person he had surrounded himself with for ten years was not a good person. They did not demand £50,000. They would have got a lot more from two newspapers.”

Speculation that the tapes included footage of a member of the Royal Family receiving oral sex was dismissed by the lawyer. He said that the royal aide in the film does describe having a sexual liaison with an MP. There is also said to be a scene purporting to show drug-taking.

The aide makes an unsubstantiated claim that the medical cause of the recent death of another member of the Royal Family may have been kept out of the public domain to prevent embarrassment.

Last night the identity of the minor royal, which has already been published in foreign newspapers and on the internet, was broadcast on American television, making a further mockery of the British courts’ efforts to keep the allegations under wraps. The Royal Forums message board carried a warning from the administrator against speculation.

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