Welcome to Moneyworld

Cash registers are ringing at Britain's theme parks, thrilling developers and children alike.

"A SIGN above the gate said 'Welcome to Bullfrog's World!' Even I was excited, and my kids were buzzing. The great metal gates swung open and in we swarmed, carried along by the enthusiasm of the crowd. And what a sight met our eyes! The place was fantastic!"

It sounds good, doesn't it? And if Bullfrog's World really existed, then no doubt the crowds would be flocking there this weekend as the nation's theme parks begin to reopen after the winter break. But the words of the satisfied customer above come from the introduction to a computer game called Theme Park, the aim of which is to construct your own imaginary park. All you need are the skills "to make people happy while simultaneously taking them for as much money as possible ... because when you play Theme Park, you're riding a financial whirlwind."

And how. Business is booming in Britain's theme parks and more and more developers all over the country are looking to play the game for real. Barely a month goes by without news of some fresh project. At the beginning of March, plans were unveiled for a pounds 500m complex at Magor, near Newport in Monmouthshire, incorporating rides, restaurants and hotels on 750 acres of land around Pencoed Castle. In February, developers of the proposed 1,000ft Festival Gardens Tower in Liverpool announced that the first 30 of its 90 floors would form a "vertical theme park" based on a jungle theme, with a 30-floor waterfall. On London's South Bank, a pounds 17m "wine theme park" called Vinopolis is expected to open next summer. And, of course, in Greenwich construction is under way on the best-known theme park of them all, the Millennium Dome.

As competition mounts, the established theme parks are responding to the challenge. Typical is Alton Towers, the country's most successful, with around 2.75 million visitors a year. Today it opens its latest ride to the public, a white-knuckle experience called Oblivion, which features a face-first vertical drop at 110km/h with G-forces pushing 4.5. It cost about pounds 12m to build and a range of merchandise includes an Oblivion condom "for those wishing to experience a second ride of a lifetime".

Meanwhile, at Legoland on Thursday, members of the press and a select group of children were granted a preview of its latest attraction, CastleLand, which also goes public today. At a cost of pounds 4m, the two-storey castle features a roller-coaster called The Dragon Ride. It's pretty tame stuff compared to Oblivion, but will no doubt prove to be thrilling enough for the park's target audience of under-12s. The minister for tourism, Tom Clarke, was also in attendance. He had a ride on the Dragon and could be seen to duck at the point where the track dips steeply down into a tunnel. "I thought I was going to be decapitated," he said afterwards.

Opened two years ago, Legoland pulled in 1.4 million visitors in its first year and has risen to third place in the theme park rankings behind Alton Towers and Chessington World of Adventures. It was built on the model of the Danish original for pounds 85m and, unlike most of its competitors, it actually has a theme. Lego bricks are an integral part of most of its attractions. And it goes without saying that Lego is the major theme of the large shop at the exit.

Since last May Mr Clarke has been taking a few days out of every month to visit Britain's leading tourist attractions (nice work if you can get it) and this was the final engagement of his tour. The minister says he's impressed by the amount of research that theme parks put into their attractions. "I think they give a lot of thought to how children react," he said. "It's all very clever and yet very simple. Kids like things that move and things that are exciting. Even today, on a very cold day, you can look around and see that everyone's very happy."

It's children who are the driving force behind the theme park boom. According to John Wilkes, general secretary of the British Association of Leisure Parks, Piers and Attractions, although parents may want to take their kids to zoos and museums, there's only one place the kids really want to go. "After the age of nine or 10, the children will take the parents where they want to go," says Mr Wilkes. "The figures show a marked movement from zoos to amusement parks at around that age."

But theme parks still have their detractors. Conservation can be an issue at new sites and local residents are often none too happy at the thought of thousands of cars descending on their country havens. This latter problem is usually countered by developers with an argument about job creation.

Theme parks really are part of the New Britain: service economy jobs, money-spinning leisure, entertainment for a TV generation, something that appeals to every class - well, the children, at least.

The appeal goes right to the top. The royal seal of approval was granted to the theme park experience as far back as 1992, when Diana and her sons were snapped splashing through Thorpe Park's Loggers Leap.

But snobbery remains. In some minds the phrase "theme park" conjures up a vision of shell-suited hordes stuffing hot dogs down their mouths. This was perhaps the nightmare vision that prompted Sir Ronald Arculus, chairman of the Kensington Court Residents' Association, to write a stiff letter to The Times regarding plans for a pounds 10m Princess of Wales garden of remembrance at Kensington Palace. "Many people would like to see a small, dignified memorial suited to the historical setting, if it could be sited to enhance and not destroy the amenities of the gardens, which are enjoyed quietly every day by local residents and visitors," he wrote. "Not a theme park, please."