The mystery of what happened to Richard Lucan, a dapper, moustachioed lord known as "Lucky", has fascinated the public for decades and speculation about his whereabouts has long been a staple of the British press.
Lord Lucan disappeared hours after nanny Sandra Rivett was found bludgeoned to death in his house in central London in 1974. A car he was using was later found on the south English coast with a length of lead piping.
It was alleged the peer had mistaken the nanny for his estranged wife Veronica, who was also attacked and fled to a nearby pub covered in blood to raise the alarm. She later identified her husband as the assailant.
Police said on Wednesday they had found the body of 80-year-old Lady Lucan after forcing entry to a house in the upmarket Belgravia area of London.
"The death is being treated as unexplained but is not believed to be suspicious," police said.
The London High Court declared him dead in 1999 and last year a judge issued a death certificate allowing his son George Bingham to inherit his title.
"My own personal view, and it was one I took I think as an eight-year-old boy, is he's unfortunately been dead since that time (of his disappearance)," Bingham said last year.
One of numerous theories about what became of Lucan, who would now be 82, was that he shot himself and was then fed to tigers at the zoo of his friend John Aspinall. Aspinall himself said in 2000 that Lucan had weighted himself down with a stone and drowned himself in the English Channel.