THE LONDON UNDERGROUND KILLER

In a South London police station, officers are shocked to discover a man has been murdered in a locked cell. The suspected killer is his cellmate, a homeless man named Kieran Kelly, in custody for theft. Police interview 53-year-old Kelly, who has a long rap sheet for petty crimes, and he calmly confesses to killing the man in the cell, but detectives are unprepared for what comes next. Kieran Kelly goes on to confess having killed dozens of people over the previous 30 years, claiming to have pushed his first victim to his death under a London Underground train.

This documentary explores what is fact and what is fiction, by talking to the those who have first-hand knowledge of serial killer Kieran Kelly, including the police detective who interviewed him and people from his past, some who never suspected their friend would become known as The London Underground Killer.