Sandra Rivett, Lady Lucan’s live-in nanny, is approximately the same height and build as her employer. She usually has Thursday evenings off but, on Thursday 7 November 1974, she is at home in the house. She offers to make tea for Lady Lucan and her daughter, Frances, shortly before 9pm, going downstairs into the basement kitchen to prepare it.
When she had not returned 15 minutes later, Lady Lucan goes downstairs to investigate. When she reaches the ground floor level, she notices that the lights in the basement aren’t working, and calls out to Sandra, at which point she is brutally attacked and hit over the head with a blunt object. When she screams, her attacker forces his fingers into her mouth to silence her. In retaliation, she grabs her assailant by the testicles, forcing him to retreat.
It is at this point that the account of the chain of events that followed diverges, according to whether one accepts Lady Lucan’s version of events, or that of her husband, as told to various people, either in person, on the telephone or in letters which he left.
Lady Lucan claims that she identified her attacker as her husband. She says that he had admitted to killing the nanny, which she surmised was a case of her husband having mistaken Sandra for herself, given the lack of light in the basement, their similar builds and the fact that she usually had Thursday nights off. Realising this immediately, and recognising the danger that she was in, she decided to play for time, allowing herself to be taken upstairs, where her husband went into the bathroom to get a cloth for her wounds. Seizing the opportunity to escape, she ran into the street and into a nearby pub, The Plumber’s Arms, where she raised the alarm and the police were alerted.
Fearing for the safety of the children, the police break into the house and discover them safely in bed. But they do find the body of Sandra Rivett in a bag in the basement, as well as a length of lead pipe, wrapped in tape, near the front door. Lord Lucan has disappeared, and a search of his nearby flat reveals only that his wallet, passport, driving licence and car keys were all still there.
Lucan had, in the meantime, tries unsuccessfully to summon the help of a nearby friend, Madeleine Floorman, and then calls his mother to tell her that Lady Lucan had been injured and instructs her to collect the children from the house. She arrives to find the police already there, and she takes the children home with her.
In the meantime Lucan takes another car, which he borrows from a friend, and drives down to the Surrey home of Susan Maxwell-Scott, a close friend, where he tells his own version of the story, which was in stark contrast to his wife’s view of events.
He says that he had been passing the house that night when, looking inside, he had noticed his wife struggling with an unknown man, at which point he went to her assistance, letting himself in and going down into the basement, where he slipped in a pool of blood. The man then ran off, and his wife became hysterical, accusing him of hiring someone to murder her. When he tried to help her, she ran away and he realised that it would be best if he left the house.
He reinforces this version with a letter to his brother-in-law, Bill Shand-Kydd, whom he had been unable to reach on the phone, in which he emphasises his wife’s mental condition, suggesting that she is suffering from paranoid delusions. He calls his mother again, and she advises that the police are at her home, asking to speak to him. He promises to be in touch the next day.
Recognizing the gravity of his position, Lucan leaves Maxwell-Scott’s home at 1.15 am in the borrowed car, and is never seen again. The car is recovered in Newhaven some days later, and the police find a lead pipe similar to the murder weapon inside. The owner of the vehicle receives a note from Lucan in the post, protesting his innocence and putting events down to unfortunate coincidences, stating that his main concern was now to protect the welfare of his children.