Mark is a good student. Intelligent and diligent, he won a place to read modern languages at one of Britain's top 10 universities. But in the run-up to his finals this summer, with a towering pile of revision still to go, the 23-year-old decided he wasn't going to be good enough. So he went on the internet, found an online pharmacy based in Turkey, and bought a pack of modafinil. It's a prescription drug given to narcoleptics, but it has also been shown to boost alertness and mental agility in healthy users. After a week of taking a tablet a day, sleeping only four hours a night, then, thanks to the drug, waking up refreshed, Mark took his exams. He got a first. Would he have done so well without pharmaceutical help? "Unlikely," he says.