Comedian Stephen Fry says he tried to kill himself after walking out of the West End play Cell-Mates in 1995.
Fry starred in Blackadder and Jeeves and Wooster
"I went into my garage, sealed the door with a duvet I'd brought and got into my car," the star reveals in a BBC Two documentary on manic depression.
"I sat there for at least, I think, two hours in the car, my hands on the ignition key."
Fry fled the country after his suicide attempt. He later paid the producers of Cell-Mates £20,000 in damages.
After returning to the UK, Fry says he was diagnosed as having bipolar disorder, which is the modern clinical term for manic depression.
"I'd never heard the word before, but for the first time at the age of 37 I had a diagnosis that explains the massive highs and miserable lows I've lived with all my life," said Fry.
"There's no doubt that I do have extremes of moods that are greater than just about anybody else I know."
'Candour and bravery'
Fry interviews other celebrities who suffer from bipolar disorder for a BBC Two documentary, The Secret Life of the Manic Depressive, which will be screened this autumn.
Star Wars actress Carrie Fisher, Hollywood star Richard Dreyfuss and British comedian Tony Slattery are among the interviewees.
The programme also talks to ordinary people who have the condition, which causes them to swing from deep clinical depression to episodes of extreme mania.
BBC Two controller Roly Keating said: "Stephen talks about his own experiences with incredible candour and bravery.
"I think he felt he could use his prominence to make a difference."
Around one in 50 people suffer from bipolar disorder in the UK.
At least one in four of them attempt suicide, with some estimates as high as 50%.
Yet the condition, although incurable, can be managed effectively with the right drug regime.