He told the Radio Times "it wasn't my cup of tea". "I felt like a drug dealer who doesn't get high on his own supply. I'll peddle the stuff but won't use it. All I did was put on a costume and act."
Firth is now starring in Nostromo on BBC2. He will soon be seen in The English Patient, the big-screen adaptation of Michael Ondaatje's Booker Prize-winning novel, and also the film of Nick Hornby's Fever Pitch.
Firth is touchy about his own romantic life. "The implication that I go around with a bimbo on my arm is not correct," he said.
He said of his year-long relationship with Jennifer Ehle, his Pride and Prejudice co-star: "It wasn't just a location romance."
He added: "It's perceived that actors go off with each other, and that is not ... entirely unjustified.The outside world disappears, to be replaced by this intense world. You don't have to worry about ... the gas bill. You just forget things."