George, Lord Bingham, who was seven when Lord Lucan disappeared, is said to have told friends he intends to have his father officially declared dead so that he can take up the seat in the Lords that has remained vacant for the past 23 years.
To do so he would need a writ in the Royal Courts of Justice declaring his father dead, on the basis that he had not been seen alive for at least seven years. The matter would also have to be investigated by the House of Lords' privileges committee, which could take two years.
Lord Lucan disappeared after his children's nanny, Sandra Rivett, was found bludgeoned to death in the family home in Belgravia, London, in November 1974. He is still wanted for questioning over the murder. Although there have been dozens of unconfirmed sightings, friends insist he is dead.
Harold Brooks-Baker, of Burke's Peerage, said: "I had heard the family were going to try and reclaim the title ... But the idea that Lord Lucan's son is going to find it clear sailing is very doubtful. I imagine it will go through eventually, but the committee will go down every single avenue to see if there is any chance his father is still alive." There were no known precedents, he said. "It is very likely there will be stumbling- blocks and I have little doubt that people you have never heard of will come out of the woodwork and claim to have seen Lord Lucan. These will all have to be investigated." The Scotland Yard file on the case is still open and David Gerring, one of the detectives who hunted Lord Lucan throughout the 1970s, yesterday said he believed the peer was alive and living in disguise in South Africa. But the Countess of Lucan, the peer's wife, who claimed the killer mistook the nanny for her in the darkened basement and was herself attacked, has said she is sure her husband is dead. Lord Bingham was reported finally to have made the decision to act after the death last month of the financier Sir James Goldsmith, who was a friend of his father.
Sir James had always denied suggestions that he helped Lord Lucan to escape, but the family are said to believe that there are now fewer doubts about the peer's fate.
Lord Lucan has already been officially "sworn dead" through a court order known as a deed of representation, which was obtained by the family in 1995. This enabled his trustees, Coutts & Co, to deal with his financial affairs as if he were dead, administering his English estate, worth pounds 150,000, meeting his tax liabilities and giving his three children their inheritance, although it did not allow Lord Bingham to assume the title.