Evidence suggesting Lord Lucan could have been murdered in the grounds of a Sussex country house will be explored in a documentary.

The question has been posed in a BBC programme to be broadcast tonight.

Makers of Inside Out spoke to a witness who contacted police claiming he saw Lord Lucan being murdered at Grants Hill House, Uckfield, soon after he allegedly killed his family's nanny in Belgravia, London, in 1974.

Lucan was seeking refuge at the house, where his friends Ian and Susan Maxwell-Scott lived.

Although the calls were investigated by detectives, it was decided no action would be taken.

Sussex Police today declined to comment on the programme. A spokesman said: "The Belgravia murder is a Metropolitan Police investigation but we will co-operate fully with any inquiry if we are asked."

There have been numerous accounts of sightings of Lucan from around the world since his disappearance more than 30 years ago.

One former Sussex chief superintendent is convinced he saw Lucan in Perth, Australia.

On one occasion police thought a skeleton found on clifftops at Newhaven may be Lucan - until a pathologist said the remains were those of a woman.

The most popular theory was that Lucan escaped to France on board a ferry from Newhaven.

But former Detective Constable Dave Wilkinson, on port duty that night, tells Inside Out that only three people boarded the ferry, none of them Lord Lucan.

Programme makers have spoken to retired Sussex police officers about the new claim.

Suspected of murdering the family nanny and then attempting to bludgeon his own wife to death, 39-year-old Lucan, a professional gambler and member of the aristocracy, fled Belgravia a wanted man.

Inside Out says that in May 1998, Sussex Police received several anonymous phone calls. All were from the same man and in each call he reported the same story.

He said he was in the grounds of Grants Hill House on the night of November 7 1974, when he witnessed three men walk from the house to the bottom of the grounds.

He said he heard two gun shots and moments later heard the sound of a splash. Two men, not three, returned to the house.

Former PC Roy Blackmore, one of the two Sussex police officers who visited Grants Hill House the evening after Lucan disappeared, said he and several colleagues saw Lucan's Ford Corsair being driven past Uckfield police station on the way to Newhaven six hours after Lucan was reported to have left Uckfield.

If true, says Inside Out, the evidence supports the theory that someone else dumped Lucan's car in Newhaven to leave the impression he had fled to France.

Forensic archaeologist Lucy Sideburn, a specialist in the recovery of human remains, has examined the site at Grants Hill for Inside Out and reveals her findings on the programme tonight.