'I like Tyrannosaurus Rex best because he kills and eats all the others,' says a tiny angelic-looking child. 'I'd like to have one as a pet'. Jamie Moss, aged six, and her brother Adam, aged eight, are waiting patiently in line to see the Dinosaurs exhibition at the Natural History Museum.

Engulfed by the heaving mass of human bodies which packs out the central hall, the Moss family from Sunbury-on-Thames seems remarkably calm. All around them, a monstrous queue snakes back and forth upon itself. Harassed officials juggle with rope barriers to keep the flow of visitors from becoming a stampede. As this wildly successful exhibition celebrates its first birthday, there is no sign of a let-up in the growing dinomania of the British public.

This year promises to unleash still more childlike passion for these overgrown reptiles. Steven Spielberg's new blockbuster movie Jurassic Park opens here in July, telling the story of a herd of exciteable dinosaurs who escape from a futuristic theme park. The merchandising bandwagon has already started to roll. Toyshops are filling up with Fisher-Price Dinoroarrrs and battery-operated brontosauruses. Computer games and Jurassic breakfast cereal are to follow. The Natural History Museum isn't resting on its laurels, either. The Dinosaurs exhibition has transformed its fortunes in a single year (visitors up by 100,000, shop sales up by 24 per cent). So what is it about dinosaurs which still appeals to the child in all of us?

The children queuing for the Dinosaurs show today have plenty of suggestions. 'What I really like about dinosaurs,' says nine-year-old Richard Howe, 'is that you get really, really tiny ones as small as an ant,' (he screws up his face tightly) 'and also great big huge ones bigger than this museum'. His arms fly out and hit his mother in the stomach. Leaping up and down at her side, Daniel, eight, has an even better answer. 'It's because,' he bellows, 'they've got teeth as big as carving knives and Tyrannosaurus Rex has 600 of them and he tears everything to bits]' 'Oh shut up,' says cousin Lindsey, aged nine. 'Some dinosaurs are nasty and some aren't. Lots of them are vegetarians.' In her notebook she has listed the names stegosaurus, brontosaurus, megalosaurus - nearly all neatly and correctly spelled.

Inside the exhibition at last, the mysterious attraction of children to dinosaurs gets curiouser and curiouser. In their Nintendo T-shirts, small boys are darting from fossil to fossil. The air is filled with a birdlike jabber of voices. 'I like scary things,' explains a tiny girl on her father's shoulders with her head wedged inside the jaws of a lifesize tyrannosaurus. Elsewhere, a row of goggling faces take in the animatronic centrepiece. Three dino-thugs with kangaroo bodies and lizard heads are biting lumps out of a diplodocus. 'Look, mum, it's trying to get up]' murmurs an awestruck boy. 'Look at all the blood] Poor dinosaur.'

It doesn't take a child psychologist to tell you that kids identify emotionally with the trials and triumphs of these weighty brutes. Professor Elizabeth Newson, of the Developmental Psychology Department of Nottingham University also explains their attraction in terms of sheer size. 'Children often say they love big animals like elephants and dinosaurs. They seem to represent a marvellous mixture of the sinister and the cosy - frightening, but also round and solid and reassuring like grandparents or guardians.' Psychologist Dr David Messer of the University of Hertfordshire inclines towards the fantasy-versus-reality explanation. 'There's a tension between the fact the dinosaurs were real once but are also pretend creatures like fairytale dragons,' he points out. 'That makes them irresistible for both children and adults'.

Many grown-ups do seem to preserve this childhood love affair. Mike Howgate has been collecting dinosaur memorabilia since he fished his first plastic triceratops from the bottom of a box of Shreddies as a child in the Fifties. He also runs the newly founded Dinosaur Collectors' Club from his front room in Wood Green, north London. 'Dinosaurs have got their teeth into me,' he confesses. 'They're just so weird, all covered with plates and spikes and three times taller than a bus. It's amazing to think that they were alive and once stomping about in Surrey and the Isle of Wight.' He thinks a lot of adults were turned on to dinosaurs in the Seventies when the theory that they were the tragic victims of an eco-disaster first became popular.

It was at about this time that the palaeontologist William Lindsay fell under their spell. 'I like dinosaurs because they give you a real sense of the vastness of time,' he explains. 'I love reconstructing the fossil animals so they have a real spark of life in them. I don't humanise them, but I do make them live in a way. For me, that's the magic.' His reconstructions of the baryonyx for the Dinosaurs exhibition took him nine years to get exactly right.

It probably takes most of today's infant visitors to the show about nine seconds to study this masterpiece of resurrection, however, before the sound effects of interactive computers distract their attention. Most distracting of all is the lure of the gift shop. Here, a frothing frenzy of small hands reach out for the dinosaur key-rings (60p), dinosaur biscuits (65p) and dinosaur kits at pounds 4.25. Indulgent parents search through piles of rubber pterodactyls to find one the right colour.

Sadly, some passionate desires are doomed to frustration. 'I want a real one,' wails a child, as his mother tries to fob him off with a red plush Stegosaurus. 'I want to look after it and keep it in my bedroom and teach it English'. The dinosaur survived successfully on Earth for 150 million years, but in young minds it has evolved into a helpless and lovable little alien. T Rex phone home?

(Photograph omitted)