Gambling is a mug’s game. And there must be plenty of mugs around because tomorrow bookmakers will take around pound;40 million in bets on the biggest horse race of the flat season - the Derby. Well, everyone likes a flutter. It’s just a bit of fun, a chance to put a few bob on a horse with a silly name, and, if it wins, that’s just a bonus.

Yes, but gambling’s also a serious, and growing, business. Four years ago, only one in five adults gambled regularly. Today the figure is nearer 60 per cent. The reason behind this huge change in our behaviour is called the National Lottery. At 40 million to one, your chances of winning the jackpot may be slim, yet more people play it than voted in the last election.

“Most people don’t think about the probability of winning,” says Dr Mark Griffiths. “They think about the amount they could win.” A psychologist at Nottingham Trent University, Dr Griffiths has spent 10 years studying the reasons behind people’s gambling habits.

The lottery has made gambling more socially acceptable, more available and more popular than ever. It has led to the deregulation of other gaming industries, advertising on television and a myriad of new ways of throwing good money after bad, from simple scratchcards to the complicated scenarios of spread-betting.

“People haven’t realised what a massive cultural shift this has been,” Dr Griffiths says. “The lottery has taken gambling out of the specialised environment of bookmakers. Now you can gamble every 60 yards down the high street.” But people aren’t likely to become addicted to it, because the twice-weekly format, unlike fruit machines or horse racing, doesn’t give them the opportunity to “chase losses”.

That, says Dr Griffiths, is the fatal attraction of horse racing, the lure that keeps hardened gamblers hooked, when “the only way to eliminate the frustration and regret is to gamble again straight away”. Research among addicts has shown that playing fruit machines stimulates the nervous system, increases heart rate and heightens levels of adrenalin.

Adolescents, who are more susceptible to addiction than any other age group, crave this buzz as a means of distancing themselves from the physical and emotional upheavals of their age, just as they might turn to alcohol or drugs, Dr Griffiths says. Chances are that they will settle down and give up as suddenly as they began. But other children will develop a long-term habit and there’s nothing in the law to stop them.

A loophole in the 1968 Gaming Act allows children as young as three to play slot machines, and the signs you see above the entrance to arcades restricting entry are voluntary rules put up by the arcade’s owners.

“The younger you start the more likely you are to develop a problem. The only way to stop that is to put the minimum age for all gambling up to 18.”

Dr Griffiths, an occasional gambler on fruit machines and football himself, is in favour of “responsible gambling”. You’re never going to eliminate its something-for-nothing appeal but the reasons why some people succumb to it more than others are more complex.

He describes it as a “biopsycho-social” phenomenon - a combination of biological, psychological and environmental factors. “The idea that gambling is a purely homogenous activity is wrong,” he says. “Every single kind of gambling activity is different.”

The one thing they have in common is this: it’s not the winning that’s important, it’s the nearly winning. The close calls (two out of three cherries in a line or a couple of matching symbols on a scratchcard) are what keep people coming back for more. So when you take your annual flutter this weekend - be lucky. And when the horse you put your shirt on comes second, bear that in mind.

CHANCE IN A MILLION

The top three sporting events in terms of stake money are this year’s World Cup (with an estimated pound;100 million gambled); Euro 96 (pound;80 million) and the Grand National (pound;70-75 million each year).

The biggest bet to be placed with bookmakers William Hill was pound;50,000 each way on a horse in the 1981 Derby. It turned out to be an also ran.

Coral’s biggest winner was a Scotsman who correctly forecast the results of 15 football matches and made pound;164,000 from a10p stake.

Overall the biggest winner for punters was Frankie Dettori. His exceptional run of seven winners at Ascot in September 1996 lostbookmakers pound;40 million and made one lucky punter pound;550,823.54.

If you fancy a flutter William Hill is offering good odds on the following: * existence of intelligent extra-terrestrial life confirmed 33-1 * man to give birth before the millennium 250-1 * Loch Ness Monster to be authenticated 500-1 * Archbishop of Canterbury to confirm SecondComing 1,000-1 * world to end at 12.50pm on August 11, 1999 1,000,000-1.

THE WINNER

Kevin Booth was a maths teacher until he started earning more from his gambling than from teaching. He now runs a telephone and Internet tipster service and lives in a 48-room castle in Scotland.

“I have always been interested in horse racing. My father - who was an accountant - encouraged me to bet a lot of money on a horse to try to put me off, but it won. I bet 3 shillings at 11-1 and won 36 shillings, which was a lot of money to an eight-year-old.

“When I was 11, with my maths teacher, I ran a book on the 1971 Derby and I cleaned up on that. I don’t suppose teachers would be allowed to do that these days.

“While taking my degree I met a few other people who were interested in racing. Most ended up in desperate straits. But I had so much money from my betting that I was lending it to them.

“I have always made it pay. There are times when you bet when you shouldn’t, so you have to train yourself to be disciplined. I bet less now than I used to do.

“Ninety-seven per cent of gamblers will lose over a year and only 3 per cent will win. But it’s the same 3 per cent every year. I thought there’s a market here for people who are losing money and who want to win. It’s a high-stress, high-risk business, but I have had a very good run for the past two years and I’m earning a lot of money.

“I can take more in a day than I could in a year from teaching. I used to love teaching and I didn’t think in terms of what I got out of it financially. But now that I’ve come to enjoy the benefits of earning money, it would be hard to go back to it.”

THE LOSER

Paul is head of history at a comprehensive in the Midlands. A gambler since childhood, he is struggling to pay off accumulated debts of pound;8,000.

“Some people smoke, some people drink. Why? They’re killing themselves but they do it because they like it. I gamble because I like it.

“It has caused me a lot of trouble. It’s a burden; it’s horrible, but it’s my own fault, I don’t expect sympathy. It’s part of me. It’s something in my nature - it’s how I am. I’m not ashamed of it.

“My mother started me off taking me to the arcades at the seaside. Me and my friends used to bet on anything - raindrops going down the window, “Bullseye” or “Fifteen to One” on the telly.

“Gambling has destroyed my life financially. It has shot my credit rating. I want to pay off the whole thing, but I can’t get a loan for love nor money.

“No one in their right mind goes into a betting shop thinking they’ll win. But if you are five lengths clear going into the final furlong it’s better than any drug you can take.

“Teaching is probably the only thing that I have really stuck at and that I’m good at. I love my job - I’m totally committed to it. It’s a difficult school and education is the most precious thing you can give the kids - it’s the only escape route they have. And if you are going to risk that then it’s not fair on them.”