A new drug of choice, ketamine, is flooding China's night clubs, and the Chinese authorities are losing the battle to stop its spread. Criminal gangs have discovered ways to make it easily and plentifully, and high profile raids and executions are not affecting soaring production. Ketamine has long been used as an anaesthetic, but now many take it recreationally for its hallucinatory highs. Celia Hatton reports for Our World on the growing addiction to ketamine. She travels to The Fortress, a village in southern China thought to be at the heart of China's ketamine production.