Sandra Eleanor Rivett was born on 16 September 1945 and worked as a children's nanny before joining the household of Richard John Bingham, 7th Earl of Lucan, and his estranged wife Veronica, Countess of Lucan, at 46 Lower Belgrave Street, Belgravia, in late 1974. Lord and Lady Lucan had separated in January 1973 following the collapse of their marriage, and a bitter custody dispute over their three children had left Lucan in financial difficulty and reportedly obsessed with regaining custody.
On the evening of 7 November 1974, Rivett went to the basement kitchen to make tea after putting the younger Lucan children to bed. When she did not return, Lady Lucan went to investigate and was attacked at the top of the basement stairs; she later stated she recognised her attacker's voice as her husband's. During the struggle, Lady Lucan asked what had happened to Rivett and said Lucan eventually admitted to having killed her. Lady Lucan later escaped the house and ran to a nearby public house, the Plumbers Arms, where she said she had escaped a murder attempt and that her husband had killed the nanny.
Police who forced entry to the house found Rivett's body in a canvas sack at the bottom of the basement stairs, along with a bloodstained lead pipe. A pathologist, Keith Simpson, determined that Rivett died from blunt head injuries and inhalation of blood, and considered the lead pipe found at the scene to be the likely murder weapon. Forensic examination found blood matching both Lady Lucan's and Rivett's blood groups on the pipe recovered at the house.
Lord Lucan telephoned his mother that night asking her to collect his children, then drove to visit friends, the Maxwell-Scotts, in Uckfield, East Sussex, where he wrote letters asserting his innocence and describing having disturbed an intruder attacking his wife. His car was later found abandoned in Newhaven; a second lead pipe, wrapped in similar tape, was found in its boot. Lucan was never located. A warrant for his arrest on charges of murdering Rivett and attempting to murder his wife was issued on 12 November 1974, with descriptions circulated to police forces and Interpol.
The inquest into Rivett's death, held before coroner Gavin Thurston, concluded on 16 June 1975 when the jury returned a verdict naming Lord Lucan as her killer — making him the first member of the House of Lords to be so named since 1760. Lucan's family and friends disputed the fairness and one-sided nature of the inquest process. Rivett's body was released to her family and cremated at Croydon crematorium on 18 December 1974.
Lucan was declared legally dead in 1999, and a death certificate was issued in 2016, allowing his titles to pass to his son. His fate remains unresolved, and his presumed responsibility for Rivett's death, while the subject of an inquest verdict, was never tested at criminal trial due to his disappearance.