There are many reasons to give up cocaine: the price, the health risks, the illegality. But for Dame Helen Mirren the decision to turn her back on the drug was more specific: Klaus Barbie.

Mirren, who won an Oscar last year for her portrayal of the Queen, says she took the decision after discovering the Nazi war criminal had been making money from selling cocaine while he was in hiding in South America in the early 1980s.

"I loved coke. I never did a lot, just a little bit at parties," said Mirren. "But what ended it for me was when they caught Klaus Barbie, the Butcher of Lyon, in the early 80s. He was hiding in South America and living off the proceeds of being a cocaine baron. And I read that in the paper, and all the cards fell into place and I saw how my little sniff of cocaine at a party had an absolute direct route to this fucking horrible man in South America."

Mirren says that from then on she never took cocaine again. "Until that moment I had never grasped the full horrifying structure of what brings coke to our parties in Britain."

In the interview with GQ magazine, Mirren, who starred in Prime Suspect as DCI Jane Tennison, says she has been held back by her looks. "I've always had big tits and blonde hair. That's an ... can be a terrible disadvantage," she said. "Because you're not allowed to be intelligent if you're a woman with big tits and blonde hair. And if you are, it offends people. Intelligence does not fit into that package, and you are patronised, condescended and insulted. Professionally."