It's one of the most audacious diamond heists in British history: despite CCTV, alarms and security guards, a six-man gang spent the Easter weekend breaking into a vault in London's Hatton Garden, escaping with the contents of safe-deposit boxes estimated to be worth millions. But how did they get away with it? Declan Lawn takes a journey into Britain's criminal underworld in search of the secrets behind the job - the creation of the team, the choice of target, the execution of the robbery and the escape plan. Speaking to victims of the crime, he asks what was inside the boxes. As the search for the perpetrators intensifies, how could they dispose of the stolen property?