A series of police blunders allowed a chef with a history of domestic violence to remain free to murder his girlfriend five years after he killed a previous partner.

Robert Trigg was only brought to justice after a campaign by the elderly parents of Susan Nicholson forced police to reopen both cases. Police finally apologised in a statement issued after a jury found Trigg guilty of the killings.

Trigg was convicted on Wednesday of the murder of Ms Nicholson, 52, who was found dead on the sofa in 2011, and the manslaughter in 2006 of Caroline Devlin, 35, whose body was discovered in their bed.