A BBC documentary will claim a mystery man was living in the house where Lord Lucan's nanny was murdered.
The man may have been the boyfriend of one of the women in the property at the time nanny Sandra Rivett was battered to death there in 1974.
The programme, due to be screened tomorrow night on Inside Out South East, claims that researchers have found a witness statement which they say was not shown at Miss Rivett's inquest.
It was made by the aristocrat's sister-in-law Lady Sarah Gibbs, who said she had spoken to the earl's daughter Camilla, then aged four.
The child told her about a man living at the house in Westminster, London, which her mother Veronica shared with her brother George and sister Frances.
She suggested he could have been a boyfriend of her mother - then separated from Lucan - but Lady Sarah is believed to have said he was more likely to have been in a relationship with Miss Rivett.
The documentary also reportedly found two police reports that Lucan was alive in 2002. But the family have rejected all the claims.
George Bingham, seven at the time of the killing, reportedly said 'If there is new evidence that is credible and from serving officers all well and good, but I very much doubt there is.
'We have been very clear with the BBC that we do not agree with what they are saving and we do not believe their claims.'
It was the first time they had been told of an alleged conversation between Camilla and Lady Sarah, according to the family.
Last February the Inside Out programme spoke to two witnesses who alleged the disgraced peer was smuggled out of the UK to a secret life abroad.
'Jill' worked for Lucan's friend John Aspinall, a zoo owner and gambling club host, in the late 1970s and early 1980s.
She claimed Mr Aspinall, Sir James Goldsmith and others held secret meetings at which she was present where they discussed getting the peer's children out to see him in Africa using second passports.
The allegations were rejected by Mr Bingham, now 45. 'So much has been written and said about my family and their links to Africa.
'There is absolutely no way my father went there. If he was going to flee he wouldn’t have gone to Africa.'
The killing of 29-year-old Miss Rivett on the evening of 7 November 1974, sparked Scotland Yard's biggest ever manhunt.
Her body was found hidden in an old U.S. mail sack in the basement of the home at 46 Lower Belgrave Street, Westminster.
Lady Lucan was also attacked and later identified Lucan as her assailant. As the police began their murder investigation he telephoned his mother, asking her to collect the children, and then drove a borrowed Ford Corsair to a friend's house in Uckfield, Sussex.
Hours later, he left the property and was never seen again. The Corsair was later found abandoned in Newhaven, its interior stained with blood and its boot containing a piece of bandaged lead pipe similar to one found at the crime scene.
A warrant for his arrest was issued a few days later and in his absence, the inquest into Rivett's death named him as her murderer - the last occasion in Britain a coroner's court was allowed to do so.