The regulars are oblivious to people around them. They hit the start button, hardly glancing at it, eyes locked on the spinning wheels. Any win is automatically reinvested. On these machines, set to win 20 per cent of the time, you could blow pounds 10 in 10 minutes without even noticing.
Serious gambling, whether on fruit machines or in the casino, on the dogs or on the races, is almost exclusively a male activity. One per cent of adults have severe gambling problems - and they're mainly men. Six per cent of children between 10 and 18 are addicted to fruit machines, mostly boys. Apart from bingo and, of course, the National Lottery (which has increased the number of adults who gamble once a week from 10 to 60 per cent), women are mainly bystanders.
And while most men will be able to control their gambling, a sizeable minority won't.
Moreover, researchers now think that, unlike social gamblers, men who gamble compulsively are indifferent to the money involved, disappointed when they win - and may even prefer to lose. Psychologists Dr Charles Warren and Dr Bruce McDonough of the Gambling Addiction Center at the University of Illinois, Chicago, recently compared the brains of a group of 16 social and compulsive gamblers. They found that the brainwaves of the nine addicts differed markedly from those of the social gamblers.
The gamblers were wired to brain monitoring devices as they played a computer gambling game. Four symbols representing card suits were flashed on to a screen in random order, with the men having to guess which the computer would pick as the winner. They could either place a bet, or not.
The researchers measured the "bet-sized effect" - what happened to the brain when a bet was placed. In the social gamblers the brain's electrical impulses, as might be expected, became more active when money was involved, indicating heightened excitement. Electrical responses became even greater with a win, and smaller if money was lost. Surprisingly, among the gambling addicts, the brain's electrical activity became milder when money was involved. And, says Dr Warren, "The really intriguing difference occurred when the gambling addicts won and there was money riding on the bet. They showed a decrease in their brain's response."
Winning, Dr Warren concluded, is almost an irritation to the gambling addict as it delays the sense of completion he feels when he loses all his money. "Winning produces a diminished response, which may drive him to gamble even more. When a gambler loses it's mildly encouraging - he just bets again. When he wins the game is up."
Could drugs help curb compulsive gambling? Scientists have found that gamblers have brainwaves similar to those of children with Attention Deficit Disorder. These children have two main symptoms - a short attention span and impulsiveness. Serotonin, a neurochemical in the brain, has been found to inhibit impulsive behaviour; if addictive gamblers have a deficit in serotonin, the obvious answer would be to give a drug which increases the activity of serotonin, such as Prozac. There are isolated reports of Prozac being given to compulsive gamblers with some success, but its effectiveness is still thought unpredictable.
Addictive gamblers have also been found to have abnormal levels of the neurochemicals thought to underlie sensation-seeking behaviours and one recent study has even put forward evidence that there may be a genetic basis for pathological gambling. Others, however, believe that it is gambling that triggers neurochemical changes in the brain, rather than vice versa.
Iain Brown, a senior lecturer in psychology at University of Glasgow, who has studied gamblers, says: "Stressful experiences and depression created by emotional events change the brain chemistry, so it may well be that being a gambling addict changes your brain chemistry too." A more significant factor, he says, is innate male aggression. To the man, gambling is not merely a game of skill, or a way of getting rich quick. "There are some gamblers - and they are all male - who get into a fierce fight to the death with a particular machine or whatever. Women tend to gamble to escape relationship problems. Men gamble for excitement, to beat the system."
Britain's 250,000 fruit machines are of increasing complexity and test a young man's spatio-visual skills to the limit. The fruit machine manufacturers understand the young male player's desire for control, says Mark Griffiths, senior lecturer in psychology at Nottingham Trent University, and build in pseudo-skill buttons which give the illusion of control.
A desire to acquire control and status are what drive men to gamble, says Dr Sue Fisher, a sociologist at the University of Plymouth who has studied the behaviour of young gamblers. "What is important to men is being able to take a loss or win - not getting too excited if you win, and taking a bad beating well. That's a male thing. It's a way of showing character, that you can take the rough with the smooth."
Alan, 42, is a solicitor and a reformed compulsive gambler.
My father gambled, my brother gambled, all my uncles and cousins gambled and I was just drawn into it. I started when I was 10 and stopped when I was 32. I gambled on horses, cards, dogs, casinos, anything. Whatever I had, I lost. When I gave up, in 1986, I owed pounds 40,000.
I'd go in to work in the morning, but the minute it came to one o'clock I was gone - down the bookies, or dog track or casino. I'd only go home when the money ran out. It affected my wife very badly. We had two young children. If our parents hadn't helped, we'd have starved. All I cared about was getting money to gamble with. I didn't care if there was food, or if the children were clothed or the bills paid.
I'd love to have a flutter now but I'm too frightened, even after 18 years, to go back to it. It's the compulsion, not the money, that's important. I once walked out of a betting shop with two sacks of money and lost it in a couple of days. It's not about winning or losing. It's about being there.