A voice coach from Isleworth is understood to be in line for a fortune, after his videotapes of Princess Diana moaning about life in the Royal Family sent tabloid style shockwaves' through the nation earlier this week.

Millions tuned in to watch footage of the tapes, which were broadcast by American channel NBC after the princess's voice coach Peter Settelen, from Jersey Road, was eventually granted possession of the 1993 recordings. On the tapes the princess mocks Charles' courtship of her, claiming he leapt on her and says he would only sleep with her once every three weeks when their relationship began.

She also claims this mirrored the prince's relationship with Camilla Parker Bowles, who she claims the prince would see once every three weeks.

After the birth of the couple's second son Prince Harry, the self-styled Queen of hearts said the two of them barely slept together at all.

Mr Settelen - a 52-year-old former actor - is understood to have been paid £500,000 for the tapes - which were the subject of a legal battle between him and Princess Diana's family earlier this year which he won.

Mr Settelen had been trying to recover the tapes since Diana's death in 1997, when he was told by Kensington Palace officials that they were missing.

They turned up again after a police raid at the home of Diana's former butler Paul Burrell in 2001. Mr Burrell was accused of theft but his case collapsed last year and the tapes had remained in the hands of Scotland Yard until a court case earlier this year.

His lawyer Mr Rutherford told this newspaper last year, when the court battle over ownership of the tapes erupted, that: "He owns them and he wants ownership back. There's no suggestion he wants to profit from them or sell them on."

But the London Evening Standard reported this week that the voice coach is understood to have gained £500,000 by selling the coverage to NBC.

Mr Settelen was unavailable for comment.