John Sweeney, a British serial killer known as the “canal killer”, has died of cancer in prison aged 69 without disclosing what happened to the missing heads, hands and other body parts of two former partners he murdered. His death closes off the prospect of answers for the victims’ families, while the Prisons and Probation Ombudsman is investigating the death in custody.

Sweeney received a whole-life sentence in 2011 for murdering American-born model Melissa Halstead in Rotterdam in 1990 and Paula Fields in London in 2001, after dismembering their bodies and disposing of remains in canals. Halstead’s torso was identified by DNA 18 years later, while Fields’ remains were found in six holdalls in Regent’s Canal; prosecutors said the missing parts were intended to prevent identification. He had also nearly killed nurse Delia Balmer in a 1994 hammer-and-axe attack after holding and raping her, and police had explored whether two other former partners who disappeared in the late 1990s could be linked to him.