Lord Lucan's son has spoken about the mysterious disappearance of his father and admitted he hoped the missing aristocrat was involved in the death of family nanny Sandra Rivett.
But in his first in-depth interview about the murder 38 years ago, George Bingham insisted he was certain his father was not the killer.
Ms Rivett, 29, was found dead at the home of the peer's estranged wife in Belgravia, London, in 1974, after being bludgeoned with a lead pipe.
The nanny's attacker turned on Lady Lucan, beating her severely before she managed to escape and raise the alarm at a nearby pub.
Lucan's car was later found abandoned and soaked in blood in Newhaven, East Sussex, and an inquest jury declared the wealthy aristocrat was the killer a year later. What happened to Lucan remains a mystery and he was officially declared dead by the High Court in 1999.
Mr Bingham, who was in the house with his siblings at the time of the attack, said it was "extraordinarily unlikely" that his father was the killer or paid somebody else to carry out the atrocity.
"People will question my judgment. Others will dispute it," he told The Daily Mirror. "But what I am certain of is dad was not the prime mover in the situation. Weirdly, however, I do hope he was partly culpable because it makes me feel better."
The former merchant banker added: "I would rather that than have my father leaving us for no apparent reason - meeting a horrible end, cold and alone, out of some misplaced sense of honour or pride that made him kill himself even if he hadn't been involved."
Mr Bingham, 45, added: "I've always thought it extraordinarily unlikely my father went into our family home, wandered down and killed anybody with a piece of lead piping for the love of his children, while those very children might well have come downstairs and witnessed this appalling carnage."
Speaking about the possibility of a contract killer being involved, he said: "Hiring a stranger, a killer no less, has to be even less likely. I've no idea of the extent of my father's involvement, guilt or otherwise, but I'm quite certain of that. Whether there was something else going on and he was involved in that, I don't know."