This machine offers a jackpot of £6 but, like every other lad in the arcade, this player is looking for the "winning streak" that could bring as much as £50.
A £1 coin drops into the machine ... then another ... four ... five. Slam, slam. Punch, punch. £6 ... £7.
Nothing. The player looks angry. He takes a quick look round to make sure that his failure has not been noticed, then skulks out on to the street.
Someone has been watching him, though. David, a lanky 21-year-old from Newcastle, has been quietly scrutinising every machine. He is looking for one that is ready to pay out.
"Watch this," he says. He steps over to the now vacant machine and feeds £1 into the slot. "It's been sleeping," he says, with a smile. He starts a fast sequence of punches and slams.
It takes less than three minutes for David to relieve the machine of £9. "It's all timing," he explains. "You've gotta know when it's ready to pay.
"It's like a numbers game. The machines are fixed and you can read patterns. When some old ladies have been pouring in their dosh for half an hour, you know you're gonna make a profit when they've gone. Most people don't know what to do to make the machine pay out."
This is not just a simple matter of opportunism; David is also a superb technician. He knows the intricacies of virtually every machine in the arcade and when the machine is programmed to pay out. In the world of the fruit machine, David is one of the elite.
Most of us are not. Still, at some time or another, we've all put a pound or two into a slot machine. There are 200,000 of them in pubs, arcades and corner shops across Britain. Every year £9bn flows into them, and £7bn - according to the fruit machine industry - is paid out (the machine takes between 20 and 30 per cent).
In reality, however, most punters keep reinvesting their winnings until they are all gone. In the end, the only winners are the fruit machine owners, a fact that provokes some critics to accuse the industry of exploiting the gullible and the mildly drunk.
At another arcade, this time in Bromley, south London, David proves his skill again by merrily winning £10. He starts off on a machine based on snakes and ladders, winning time and time again to come out £7 ahead. Next, he moves on to an old-fashioned "noughts and crosses" machine.
He warns against doing the obvious: taking up the machine's invitation to hold the reels; time and time again he's proved right. No stealth or subterfuge, just solid knowledge. This time, he's £3 ahead - £10 in just 13 minutes.
David is one of a growing number of unemployed young people who spend their days touring arcades, cash in pocket, "working the bandits" and waiting for gullible tourists to empty their pockets into the machines. Some work in teams, others in pairs, sharing their knowledge and skills. David knows most of them, but chooses to work alone. "Less hassle, most return," he says.
"I've graduated. I don't want no more of that posing and strutting about. You know, showing off to the young kids. It's a waste of money."
David started his career, aged 17, as a part-time attendant in an arcade in Blackpool. He had always loved the machines, but the experience of working with them got him hooked.
"It really got me in, and I got to know these kids who made good money off the machines. All the jobs I'd done sucked. This is my profession."
David learnt the hard way, losing money night after night. Every symbol on every reel of every machine had to be learnt through trial and error: an expensive business. Soon, however, he became what sociologists call a "king", with an entourage of small boys. After two years having fun but losing money, he decided to "become professional. I had all this stuff I knew, it was all in my head so I figured I'd work smarter".
The arcade owners know David's business, and they don't like it. The two play an elaborate cat-and-mouse game. Arcade attendants occasionally move him on, but David is artful. Like the management of any casino, arcades work on the principle of watching people watching people, and David knows this. Most arcades have rules that stop people "hanging about and watching". Some, such as the Sun Valley chain, even prohibit people playing more than one to a machine, which stops the players sharing their skills.
David is on a circuit during the summer, spending his days in the seaside amusement arcades in Blackpool, Brighton and Ramsgate. At other times of the year he sticks around London, where he has a "run" of about 20 arcades. In this way he manages to supplement his dole by £200 a week, sometimes more.
David is one of the few winners in this game. "Most people are idiots," he sneers. "You can't win if you keep putting your money back into the machine. OK, sometimes you can get 20 or 30 quid in a big win, but I usually quit after 10 quid. That's smarter."
Dr Mark Griffiths, a psychologist at the University of Plymouth, spends a great deal of time at arcades and writing elaborate papers on the fruit machine industry. He says manufacturers deliberately incorporate features that mislead players into thinkingthat they have a good chance of winning. The machines may seem "fair" and "random" but that is just an illusion.
"Many of the machines are designed to make the player feel that a win is near," says Dr Griffiths. "These machines provide a constant sequence of exciting events that keep the player involved. They are designed to give a great many near misses. They alsogive a false impression that the machine can be beaten by skill. In reality, a lot of the activity is controlled by a microchip."
John Wain, head of Britain's biggest machine manufacturer, Barcrest, could not disagree more. He starts off by claiming that Dr Griffiths is just plain wrong, but eventually admits: "Our machines aren't entirely random."
So when aren't they random?
"On the payout." Pause. "We can do this," he adds hastily, "It's within the law."
Dr Griffiths says attempts to "beat the bandits" have become quite sophisticated. Some players appear to have a system called a "winning loop" - they refuse to hit the "gamble" button, regardless of the temptation, which confuses the machine, inducing itto pay out continuously.
Back in London, David denounces the fruit machine: "Anyone who puts more than a pound in at a time is a mug".