Lord Lucan probably committed suicide in the Channel after leaving Britain, according to his best friend.

Casino owner and conservationist John Aspinall, one of the last people to see Lucan before he disappeared, said he believed the earl's bones were lying "250ft under the Channel".

He told The Sunday Telegraph that this was the first time he had spoken about the peer's disappearance on the record since he was interviewed by the police in 1974.

"He (Lord Lucan) tied a stone around his body and scuttled the powerboat he kept at Newhaven and down he went. I think it's a very brave thing to have done," he said.

Mr Aspinall, 73, who is dying of cancer of the jaw, added that he had no doubt his friend had been guilty of bludgeoning his children's nanny to death after mistaking her for the wife he plotted to murder.

"The tragic thing is that the innocent nanny should have got killed," said Mr Aspinall.

"Lucan killed himself out of shame for having botched it. He reckoned that if he wasn't around any more, there'd always been a question mark over his guilt, which would be good for his children."

The peer was officially declared dead by the High Court last year.

His blood-soaked car was found abandoned in Newhaven in 1974, the day after the battered body of his children's nanny, Sandra Rivett, was discovered at the earl's family home in central London.

Mr Aspinall's interview came after a zookeeper was killed earlier this week by an elephant at one the wild animal parks he owns.