During the trial of former butler Paul Burrell, it emerged that Diana, Princess of Wales, had kept a cassette tape containing details of the allegation.

The tape, which supposedly consisted of an interview Diana conducted with the alleged rape victim, went missing from a locked chest in Kensington Palace and has never been found, the Old Bailey jury heard.

No evidence was forthcoming in support of them and the person concerned did not want to pursue the matter any further.

St James's Palace

A spokeswoman for St James' Palace issued a statement in relation to the allegation that one of Prince Charles's male members of staff was raped by one of his colleagues.

The statement said: "Between October 2001 and February 2002 there was a full police investigation into events alleged to have taken place in the late 1980s.

"When these allegations first emerged in 1996 they were investigated by the Palace and no evidence was forthcoming in support of them and the person concerned did not want to pursue the matter any further.

'No further action'

"The allegations re-surfaced and a member of the Royal household was interviewed by police voluntarily in November 2001.

"After a thorough review by the police, the Crown Prosecution Service and the Director of Public Prosecutions himself the investigation was confirmed as completed and no proceedings were brought."

A Scotland Yard spokesman said: "In July 2001 we investigated an allegation of sexual assault.

"A file was submitted to the CPS and in February 2002 we received advice from the CPS that there was to be no further action.

"The inquiry is inactive but, as with any case, the file is still open and if further information comes to light we would investigate it."