How one of the first Tesco Clubcards was used to pay off a blackmailer threatening to poison frozen food. And how that Clubcard was used to catch him.

Presented by journalist and true crime documentary maker Amber Haque and criminal psychologist Dr Julia Shaw.

Producer: Ciaran Tracey with help from James Shield Executive Producer: Innes Bowen Production Coordinator: Juliette Harvey Mix Engineer: John Scott Commissioning Editor: Dylan Haskins Assistant Commissioner: Izzy Lee-Poulton

Bad People is a BBC Studios production for BBC Sounds