For millions of people across the world, lighting up a joint is no more controversial than having a cup of tea. But in Hash Wensley Clarkson explores the dark and sinister side of this multi-billion pound business: one fuelled by a brutal underworld network of dealers, drug barons, bent cops and even terrorists. Sex, intimidation, bribery and murder are all employed in a quest for vast profits.

Travelling from the lawless Rif mountains in Morocco to darkened warehouses in Spain, protected by heavily armed gangsters, this is a revelatory roller-coaster ride through the secret world of Hash.