Alastair Campbell, Tony Blair's spin-doctor and "the second most powerful man in Britain", as he was once dubbed, knew something was desperately wrong when he found himself driving a hire car endlessly around a roundabout.
Only 28 and the news editor of a national Sunday newspaper, he was drinking "from day to night". The result was a "work-induced, drink-induced, pressure induced, depression-induced psychotic breakdown".
Twenty years on, Mr Campbell, who went on to become a key member of Tony Blair's inner circle, vividly remembers the day he "cracked" and ended up on a hospital ward after being arrested. "Your mind is like plate glass and you are trying to carry it around and hold it together and you feel it cracking. It's getting bigger and bigger and you can't hold it any longer and it explodes."
This Tuesday is World Mental Health Day, and the father of three, who was the Prime Minister's director of communications for more than seven years, is speaking exclusively to The Independent on Sunday about his own experiences with depression in an effort to remove the stigma attached to mental illness.
"There is a tone of bereavement when people talk about mental illness. We have to get to a position where it's talked about it in the same way that you talk about a broken leg.
"I was very depressed for a long time. You wake up, can't open your eyes, you can't find the energy to brush your teeth. The phone rings and you stare at it."
Today, Mr Campbell is teetotal: he acknowledges that alcohol was one of the factors in his breakdown. It was only when a friendly young psychiatrist at the hospital asked him about his drinking that he realised he had a problem.
"I had always drunk a lot since I was a teenager, but like a lot of people with drink problems I was not really aware of it," he says.
"I didn't drink because I was shy or anything, but my father is from the Hebrides and there is quite a big drinking culture. Newspapers... there is a big drinking culture.
"My family and friends tried to warn me, but that made it worse. I always denied I had any sort of problem until two or three days into the hospital treatment and this very nice psychiatrist asked me what I had to drink. I went through it and it suddenly dawned on me I was drinking from day to night. It was affecting my work and life at home."
His recovery was "a slow process" which took "months" and involved medication. But he was lucky to have the support of colleagues, his family and the man who is still his doctor, whom he describes as "fantastic, brilliant".
"It was unbelievably scary. At one point, I thought I was going to die. We didn't have kids then but it was very, very hard on Fiona [his partner]. I was at the Mirror, very comfortable spiritually, and was only 28 and I got flattered into this taking this job as news editor at Sunday Today. I didn't feel at home there at all, and I was not ready for it.
"I was allowed to take as long as I needed to take to get well , which was months."
Then came the Downing Street years. Mr Campbell says he had sorted himself out and had emerged a much stronger person mentally. But with power came huge pressures.
"When I worked for No 10 I had periods when I knew I was depressed but you just have to keep going. It's hard because of the energy levels required and the crash you have after."
The whole period of the Hutton inquiry and the tragic death of Dr David Kelly put him under intense strain, which he describes as the "worst period".
"I did feel if the inquiry had gone against us that it would have been grim, really bad. Part of me was thinking about that a lot. Again it was one of those episodes where things spiralled out of control.
"Let's be brutally frank: if it had gone against us... it wasn't just me who was out of a job, it was Tony. It was a phenomenal pressure. The blood they smelled was mine.
"I felt completely confident in relation to the facts. But during the whole period it was a nightmare. And also you are thinking, 'There's this guy for whom it's been such a nightmare he's killed himself'. The day he died was without doubt the worst day. It was about the sadness that someone felt driven to do this.
"The mentality I was adopting as I walked through was, 'This is not as bad as where I've been.' At points of real pressure I always say to myself this can't be worse than 1986.
"Fiona finds it a bit shocking when I say this, but my breakdown was one of my worst and best experiences - the worst was the feeling of losing myself totally. The best was because it sorted out who I was and what I wanted to do."
What concerns him now is the portrayal of mental illness, especially in the media. "The most worrying thing is the constant association between violence and mental illness. There is a lot in the papers about lifestyle but very little about mental health. Three to four years ago there was the Frank Bruno headline in The Sun. Last week it was "Lunatic at No 10".
"What is your instinctive reaction when you see a wino? You sometimes feel fear because there is a chance they can be violent, you think, there but for the grace of God... But you rarely think, this is someone with a mental illness."
"I know people with serious mental problems who spend years holding down a job before telling employers. If you are upfront [about mental illness] it's going to get held against you. This is one of the reasons I'm happy to talk about how it affected me. I was lucky."