Outings: 'I have seen the future of fun. And it works. Sort of'

On the map of the world that every cheap thrill-seeker carries around in her or (more likely) his head, London has just been catapulted from nowhere to the premier league of theme-park venues. Ever since Battersea Funfair closed down a generation ago, packaged fun has been largely absent from the capital. But with its new high-profile, high-voltage presence at the London Trocadero, Segaworld aims to turn the theme-park world upside- down virtually overnight.

The word "virtually" is used advisedly. Theme parks devour cubic metres, consuming space with ever more extravagant rollercoasters. Why not, went the thinking at the Japan HQ of computer games company Sega, create an inside-out thrill palace? The cutting edge of technology can carve out a new universe where nothing is quite as it seems. Imagination supersedes engineering; electronic introspection replaces the extrovert exploration of g-forces. That is the premise behind the most significant addition to London's tourist stock of the Nineties: the creation of Europe's only virtual reality theme park in the heart of the capital, a couple of hundred yards from Piccadilly Circus. I have seen the future of fun, based on the silicon chip, and it works. But only sort of.

The term "upside-down" is used advisedly, too. I spent (too) much of Monday evening in an inverse position, zapping aliens while I dangled from the discomfort of the R360. This miracle of gadgetry comprises a kind of tumble drier cranked up to human size. You are strapped in, instructed to take off from an illusory aircraft carrier and shoot down as many of the enemy as possible in four minutes while rotating rapidly around an axis or three. Too late, I realised that the 360 indicates the number of degrees you pass through. But then, the theme of virtual mayhem reverberates throughout each of the seven levels of Segaworld.

The other motif is queuing. At the ground-floor entrance, I lined up for five minutes to hand over the steep pounds 12 admission. The wait provided a chance to assess my fellow thrill-seekers. Whatever Sega may have anticipated as its target market, the majority of people queuing at teatime on Monday were in their early twenties. They were overwhelmingly male. And intimidatingly tall: at six-foot-two (183cm), I was the shortest person in the line.

Height becomes an important issue when deciding how much you pay - and what attractions you are allowed on. You have to be at least 110cm (3ft 7in) to use most of the rides, and 130cm (4ft 3in) for the best experience in the whole place, my inverting friend R360.

Altitude does not discriminate against the sensory overload, which begins as soon as you enter the atrium with a dazzling and deafening explosion of light and sound. Tardis technology has evidently been employed to expand the old shell of the Trocadero by a dimension or two, and the effect is startling. You leave the ordinary tourists several floors below and ascend to the top of the Troc by means of two exaggerated escalators, feeling like an extra in Bladerunner, while a battle of neon and laser, glass and steel is fought around you.

Then it all starts going awry. I waited half-an-hour (not the promised 15 minutes) for a close encounter with the Beast in Darkness. At the front of the queue, a cheerfully theatrical Sega operative warns you that a murderous monster was on the loose. He demands to know if you are truly brave or merely stupid. After a pulse-pumping walk through a compendium of scariness (including trudging across something that feels suspiciously like industrial Play-Doh), you climb aboard a moving chair.

With that thrillseeker's rush of excitement mixed with a gnawing queasiness, I tensed in expectation of virtual terror. It never arrived. The aimless three-minute trundle around a small, dark chunk of London WC2 was not so much thrillus interruptus as virtual impotence.

I suspected a teething problem with the machinery. "My screen's not working - I couldn't see anything apart from the exit signs.

"You're not supposed to," explained a vaguely ghostly voice in a yellow T-shirt. "It's an audio experience."

What I thought was, "You mean I waited 30 minutes for that pathetic collection of sub-Radiophonic Workshop sound effects? You're taking the mick."

What I said was, "Oh."

Your slow descent back to ground level employs a labyrinth of junior escalators, designed to lead you through what I suspect is the financial raison d'etre of Segaworld. Your pounds 12 investment (pounds 9 for under-16s) entitles you to use the half-dozen rides as often as you like, or have the patience to queue for. But there are hundreds of other, smaller machines for which you have to pay per play.

The first stop is a gallery called the Combat Zone: basically a well- to-do amusement arcade, where the deadly serious business of zapping aliens can be carried out on a dozen all-flashing, all-beeping machines. Last Monday evening, you could exterminate invaders all night for free. But setting all the machines to Free Play appears to have been an introductory offer. Once the opening honeymoon is over, five minutes of miscellaneous massacre will cost pounds 1.

Onwards and downwards. The waiting time for Aqua Planet ("a 3D interactive motion adventure") was showing 45 minutes. I calculated this would devour far too much of the four hours that Sega reckons you need for the whole theme park. The queue for the adjacent Space Mission was a more modest half hour. So I joined it.

Forty minutes later, I was strapped in and ready to go. Thirty people at a time are loaded into spaceships and equipped with wraparound headsets. This was what I was waiting for - an exploration of the final frontier in fun, where a clever combination of screens and sounds persuades you that you are the rear gunner for an intergalactic spaceship. After a bit of joggling around and some unconvincing visual effects, I was still frustrated. The impression must have been much the same when television was invented. You are thrilled that the thing exists, but wish it could work a jolly sight better.

And another thing: why do you always end up shooting aliens? Parents need not be particularly pacifist to fret about the emphasis on electronic violence, and the parallel implication of indestructibility. I laughed my disoriented socks off when I crashed the R360 tumble-drier on landing, and emerged with no more damage than an overextended grin. On the Race Track level, I did dozens of laps of the Isle of Man TT Circuit, racing virtually around on a high-powered motorbike. Given that I am shaky enough on a bicycle, I inevitably crashed once a circuit or so. After a bit of hi-watt hyperactivity on the part of the machinery, you land safely back in the saddle and roar off once more. If that is the message that 17-year- olds are picking up, God help them should they buy their first Honda and expect the same degree of forgiveness on the roads of the real world.

This worry is not restricted to Segaworld, of course, since similar machines can be found in amusement arcades all over the country. Segaworld's Unique Scaring Proposition rests with the big rides, like the Ghost Hunt. The good news is that there is no queue. The bad news is that this ghost train ride to nowhere is about as scary as Thomas the Tank Engine in a mild grump.

By now you are running out of time and patience. So you pin your hopes for being terrified on the Mad Bazooka. But the 30-minute wait for it just makes you mad when you realise that these "Hyper Battle Carts" are dressed-up dodgems, and not as much fun as the ones at Butlin's in Bognor either - despite the electronic chance to destroy your fellow dodgers.

All that zapping makes you hungry, so it was something of a relief to find McDonald's (and I never thought I would ever write that). Equally pleasing is the discovery that a Big Mac, fries and Coke weighs in at pounds 2.88, exactly the same as outside on Shaftesbury Avenue. Don't try this immediately before another tumble-drying, alien-blasting session on the R360, though.

The Segaworld staff were uniformly helpful and friendly, including the chap at the exit who was conducting a satisfaction survey. No, I didn't think it was good value for money. No, I probably would not return. An upside-down glance at his survey results so far revealed that I shared the majority view.

"Try telling your brain it's not real," goes the Segaworld slogan. Don't worry - your empty wallet will assure you that it is all too genuine. I hoped pounds 12 would buy things that made me go "Wow". Instead, I mostly found stuff that made me say "Oh".

Those cheap thrills are just too expensive.

Segaworld is at the Trocadero, on Coventry Street just east of Piccadilly Circus. It is open from 10am to midnight, daily except Christmas Day. Over-15s pay pounds 12, children 15 and under pay pounds 9.