Britain's newest theme park doesn't officially open until Friday. But Tracey Garner got a sneak preview, thanks to her son Jack
Modern-day theme parkery is a funny business. We send a Brit, Trevor Davies, to mastermind the year-long culture thrill ride in Copenhagen, European Capital of Culture for 1996. In return, Denmark sends us Legoland. The maker of the plastic bricks has a long-established original in Billund, a small town in the middle of Jutland (and nowhere). The Danish invasion is the latest attack in the theme park war that is gathering momentum and g-forces across England, a country already endowed with a much higher occurence of thrills per hectare. Can Denmark's audacious opening next week - so close to Her Majesty's home - attract the nation's fun-seekers? I took my son Jack, aged eight, to find out.

Lions, polar bears, lizards and the like can still be found on the old Windsor Safari Park site, but these are now creatures of the Lego kind - painstakingly pieced together out of millions of those little plastic bricks, which many a mother will recognise as the things that hurt like hell when you tread on them and are a nightmare to get out of the Hoover's innards. The preview day on Saturday, ahead of next Friday's public opening, was exclusively for members of the Lego Club. It was billed as an opportunity to road test the park - in trade terms, a "soft opening" to iron out problems before the big day. Pay the discounted admission of pounds 10, and be among the first kids on the new blocks.

So all the people who flooded in at 10am last Saturday were already Lego aficionados. The models certainly lived up to their expectations. Attention to detail is paramount: bright plastic birds in the trees, an injection- moulded boy attempting to retrieve his kite from the roof of a building, even a built-by-numbers dog relieving himself against a real tree. Twenty million bricks alone are used to recreate the cities of Europe, not counting the ones that are no doubt stuck down the back of the company sofa.

But putting the bricks to one side for a moment, what else is there to do at this latest addition to our growing band of theme parks? If you go expecting white knuckle rides and roller coasters, you'll be sadly disappointed. Rides are few and far between, and unashamedly aimed at the under-12s. The chance to drive your own Lego car (with the promise of a driving licence at the end of it) and piloting a boat along a snaking river were probably the most popular attractions, and the queues built up quickly. A hot summer Sunday could be quite an ordeal.

There are several areas for children to play with bricks. One excited chap grasped a couple of motorbikes, vrooming them enthusiastically along a mini road with full sound effects blasting from his mouth, while his son played quietly in the corner. As ever, the children's adventure play area fails in the way of many theme parks: a serious lack of seating for parents (the ones who don't happen to be playing with bricks).

Every theme park has to have live entertainment, and Legoland's are a mixed bag. The harbour show was superb, with five enthusiastic sailors enacting the Mystery of the Missing Lego Bricks (down the back of the sofa, surely?), and leaping into freezing water from the top of a 30ft lighthouse to rapturous applause. It's probably best to draw a veil over the other shows in the hope that when "Overture and Beginners" is called on opening night, the acts will have been polished up.

And beware of the maze: it's not as tame as first appearances might have you believe. The Danes obviously get a kick out of sending jets of water up the trouser legs of unsuspecting visitors. Few found it funny on a freezing March afternoon, including the toddler found in the ladies toilet whose Mum was desperately trying to dry off his clothes under the hand dryer.

The Lego Shop - which is strategically positioned at the exit - stocks an unequalled range of all things Lego; from computer mouse mats to a pounds 35 tie. But from about 4pm onwards the shop and its tills seemed inadequate under the challenge of hoards of departing visitors digging deep into their pockets. I'm sure I wasn't alone in promising my eight year old a trip to Toys 'R' Us the next day instead of standing in the unmoving queue.

When it came to sampling the restaurants and cafes we breathed a sigh of relief that we'd opted to bring our own picnic. Queues did trail out of the doors, but as the day was heavily billed as "a chance for us to try out procedures", grumbles about inexperienced staff and equipment failure can be forgiven as teething problems.

However, the most important opinions are surely those of loyal Lego Club members. Eight-year-old Jack, who should own shares in Lego if the thousands of bricks piled up in his bedroom are anything to go by, had this to say: "I thought the models were excellent. They had lots of detail, lights flashed on them and some moved, like the giant spiders legs. My favourite models were in the Technic rock 'n' roll band which were worked by a Lego mechanical system. It must have taken years and years to build all the models. The shop should be bigger to take all the people. The panning for gold, which cost pounds 1, made my hands cold, but I got a Lego medal for the gold I collected. I loved my driving lesson, but I was sad there weren't any big rides like the ones at Thorpe Park."

It's good to welcome a new theme park to add to the "How do we entertain the kids over this school holiday" list, but Legoland Windsor's failure to provide enough entertainment for the adults and older kids bodes ill for return visits - seen it, done it, what's next?

Starting blocks:

Legoland Windsor (0990 626375) opens to the public at 10am on Friday morning and daily thereafter until the end of September, plus weekends and half-term in October. The park closes at 6pm, with late opening to 8pm in July and August. Adults pounds 15, children aged 4-15 pounds 12, aged 3 or under free. Discounts of pounds 1 if you book in advance on 0990 626364.