“At my lowest ebb, I was drinking 12 to 14 bottles of wine and doing five grams of coke per day,” says Mark, a 47-year-old from London, who runs his own successful business. “I started out using it because I wanted to be a party animal. Then I used it to cope with the stress of work. Eventually I lost all control and became a total recluse, staying at home to snort coke all day.”