Police have refused to release documents into the murder investigation of the nanny of Lord Lucan because they say the earl may still be alive.
Lucan, who has been legally declared twice, still remains a suspect in the death of Sandra Rivett who was found bludgeoned to death in November 1974 and his estranged wife injured, London's Metropolitan Police have said.
It followed a request by the Mail on Sunday for documents into the first 10 years of the murder probe.
Lucan went missing after the nanny's body was found and later his wife, Lady Lucan, named him as the killer.
The speculation was that he had meant to kill his wife as he was battling for custody of their children and killed the nanny by mistake.
As one of the greatest mysteries of the age, there were claims he had been spotted in the last four decades but he has never been caught.
A Met spokesman said: "There is no definitive evidence to support that Lord Lucan is dead or still living. The investigation into the murder remains live".
Lawyers for the police said, according to the Sun: "Lord Lucan is still very possibly alive and remains an outstanding murder suspect. Although there has not been any proof of life there has neither been any indication of evidential/tangible proof of Lord Lucan's death.
"There is statistically a very reasonable chance that he would still be alive."
Lucan's son George Bingham said he believed his father had committed suicide. His wife, Lady Lucan died in January, allegedly at her own hand after she had diagnosed herself as having Parkinson's disease.
Lucan was declared legally dead in 1999 and a second high court ruling in 2016 also concluded that he was deceased.