The family of a violent gangster who was the prime suspect in the mysterious death of a London teenager which has sparked a best-selling book and forthcoming major TV adaptation have spoken for the first time.

Zac Brettler, 19, jumped from the fifth floor of a luxury riverside apartment building and was found dead in the Thames six years ago – while notorious gangland enforcer Verinder Sharma, known as ‘Indian Dave’ was the only person present.

The mystery surrounding the death of the middle-class public schoolboy from Maida Vale is explored in a new publishing sensation, London Falling: A Mysterious Death in a Gilded City, which hit the shelves last month and has become a global best seller.

The book tells how fantasist Zac pretended to be the son of a Russian oligarch personally worth £200million and attracted the company of some very shady people determined to get their hands on the imaginary money.

Now, for the first time, members of the gangster’s family have spoken about what happened – and revealed that Zac’s death may have come shortly after furious Indian Dave found out that the money didn’t exist.