Regrets: Trader Nick Leeson brought Barings Bank down in 1995 with fraud was jailed for six-and-a-half years
Clean-cut: Leeson suspects Kerviel incurred the £3.7billion loss over a substantial period
When markets are going your way, the feeling is brilliant - more intoxicating than champagne, more exhilarating than sex.
A successful trade makes you feel invincible.
But when things start to go wrong, you hide your losses and blithely try to carry on in the hope that you can recoup them.
You can't tell your colleagues that you've lost money - the macho ethics of the trading desk do not tolerate admissions of failure. You certainly can't tell your wife that your high-end life is at an end.
It is as if you are slipping into a personal abyss as the panic begin to eat at you.
The only way back is to bet more, risk more - and lose more until there is no hope of return.
That's what I felt back in 1995. So I experienced a sickening twinge of recognition when I heard of Jerome Kerviel's £3.5billion loss at Societe Generale.
Here, I thought, was someone going through exactly what I had experienced.
When you are losing such vast sums of money, you try to carry on in the misguided belief that can beat the market for a couple of days. But, in the end, the market always breaks you.
Of course, you may have a few good days when the markets go in your favour and you are persuaded that you can make the money back.
You still think you can pull yourself out the nightmare and get back to a break-even position. But ultimately you are living on borrowed time.
To work in such fast-paced environments, the City attracts a certain obstinate and compulsive character - especially in the derivatives market where Kerviel and I worked.
The truth is that banks need people with confidence who enjoy taking risks - traders who are prepared to gamble by betting on futures which their rivals might be too to timid pursue.
Then there's the intensity of trading on electronic systems which hold you in a trance.
You are watching up to ten screens at a time for the smallest change in the numbers as they update themselves every second, as Kerviel would be doing monitoring the French and German indexes and their main stocks.
When things start to go wrong, the creeping, paralysing panic takes hold. At first, you just shut down your browsers and walk away and seek a bit of light relief.
It's as if you are in a parallel universe. In the false world outside your head, all is well; everyone's celebrating their good times, your wife and family are enjoying the fruits of your success.
in your private world of mental turmoil, there is only a gnawing fear.
You realise you are going to lose your job and everything that goes with it.
You are going to lose the respect of your family. You're probably facing time in jail.
You are juggling two totally opposite worlds, trying to keep the positive things alive.
Drink often becomes a way to escape, although not in my case.
A marriage ought to bring you back to reality. But the danger is that your wife is too heavily committed to the success story and the enjoyment of all its trappings.
How can you break it to your partner - and your kids if you have them - that the car's going to be returned, the house is going to be repossessed and that your name will be a byword for failure around the world?
You don't want to let them down - which makes it harder to face up to the truth and stop trading.
Fortunately, I didn't have kids at the time, but I lost my wife.
I have since remarried and I'm grateful that my children grew up knowing the real me rather than the newspaper and film image.
One of the problems with success is that it creates a feeling of unthinking omnipotence.
Not only have you made millions for your bank and earned the admiration of your peers on the trading desk but you have also beaten hundreds of the smartest financial brains on the planet.
But at the back of everyone's mind who works the financial markets is an unspoken fear of failure.
Indeed, there are plenty of traders who go on to the trading floor after smoking cannabis to calm themselves down.
Equally, the bank bosses never want to talk about risk systems or how they might avoid mistakes and save money.
They simply want to know how traders are going to make more millions.
A bank's trading desk is like a tribe - the smartest and most powerful tribe in the financial house's building.
A perfect example of this sense of teamwork was the case of John Rusnak, a trader with a U.S. subsidiary of Allied Irish Banks who placed large oneway bets that the yen would rise against the dollar and lost £345million.
At the time, everyone bought into his success story and failed to spot the danger signs.
But the tribal loyalties are very frail. When in trouble, you cannot turn to someone close to you in the office for support.
At the height of my losses while working for Barings, I remember coming back from Singapore to England and having a family dinner.
No one knew what was going on at that point. I kept sneaking away to be sick out of pure fear.
Telling my family the truth, I thought, would be far worse than returning to face the markets.
Although I eventually fled to Malaysia, Thailand and finally to Germany, I had still never admitted to anyone by the time I got off a plane at Frankfurt airport what I'd done.
I never even told my wife, Lisa. Everyone had to read the truth in the newspapers.
This latest loss of £3.5billion is an awful lot of trouble to get yourself into. I do not believe that the losses were racked up over a short period. It took me three years.
I also don't believe that no one knew that it was going on. For the bank to ignore that degree of exposure stretches credibility.
For me, I took 100 per cent of the blame for what happened at Barings. I knew what I was doing and I realised that I shouldn't be doing it.
Traders are highly intelligent people and anyone who makes a mistake and claims they didn't know what they were doing is not being honest.
Of course I didn't know how catastrophic my actions would be for Barings and that I would destroy the bank.
It was simply a case that the losses that I had incurred got so big that it was impossible to unwind.
It took me a long time to return to normal, to look at people I respected in the eye.
For years I avoided looking at stories about firms losing large sums of money - I just couldn't bear being reminded of the horror I'd been through.
Only now I can look back and try to understand what happened. It will, I predict, be a long time before Kerviel will be able to do the same.
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