The most spectacular items are some large landscaped working models, where miniature big dippers swoop and trains whizz in and out of tunnels and over viaducts. Rows of tiny smudges along the various protective glass screens testify to that day’s quota of juvenile noses pressed up hard to get the best view. This is not a place pupils willingly leave.

Other themes include ships and boats, a traffic room plus sound effects, and a games room where children can play an enlarged and electronically adapted Victorian version of Snakes and Ladders.

A nursery room contains a unique Peter Pan collection on loan from Great Ormond Street Hospital. It was in Kensington Gardens, around the corner from the museum, that Barrie met the children who were to inspire his great drama. When the adjoining Round Pond was recently drained for cleaning, dozens of rusted wrecks of tin boats were found on the bottom: testimony to the way that toy propeller shafts so often let water seep in with fatal effects.

A room given over to military toys has the atmosphere of a First World War trench. Later fighting equipment or personnel on display (made in the l930s) remind visitors that toy-shops started to re-arm well before the Second World War. What sort of war toys are shops stocking now?

Elsewhere a working model of a fun fair takes up a whole room of its own. It features over 350 individually dressed figures against a background of different attractions that whirl around to accompanying music. Like other models in the museum, it was made earlier this century and exhibited on piers or in fairgrounds before finally coming to rest in the safer surroundings provided here.

The grand finale of the museum is Baywest City a six-metre model containing trains, helicopters, sky-scrapers and the unexpected arrival of a spaceship that gently settles itself in this urban sprawl once it has been found to be friendly. The disc-jockey Simon Bates adds an explanatory commentary throughout this episode. Children watch all this on a wall-length diorama with special television screens to help. Baywest itself is an amalgam of Piccadilly and San Francisco, and is built from plastic. Human figures measure one centimetre but, when viewed as if from 300 feet above, could well be real, along with everything else.

In the garden, a model railway offers rides alongside smaller gauge tracks with their own train services; some interesting problems of scale here. There is also a hand-cranked merry-go-round dating from 1920.

Other entertainments have a more educational bent. Hands-on sessions with the staff using replica or duplicate models allow groups of pupils to examine old as well as new toy technology, with clockwork mechanics often proving fascinating in their own right to today’s electronically-oriented child.

There is also a time-machine experience, where the lively young curator, Hamish MacGillivray, dresses up as a benign Victorian toy-shop owner. He then shows pupils the toys that rich merchants’ children could expect around Christmas. Examples are drawn from mock toy-shop windows from the past, including famous names like Hamleys and Gamages.

Pupils are then led into a working pithead and coal mine model. Built by a South Wales miner and his wife more than 90 years ago, lifts plunge, 200 miners dig and their pit ponies haul loaded wagons. Tiny Davy lamps sparkle in the dark; visiting pupils, sometimes dressed in Victorian costume when schools and parents have made the effort, can also wear their own Davy lamps.

Above the mine, surface workers mingle with others waiting their turn to go down. Pupils are asked to guess what sort of toys poor miners’ children might once have expected. Their answers so far have not been optimistic. An excellent resource book for teachers on the coal mine is available from the museum’s educational services.

These hands-on sessions also cover history and technology as required by key stages 1 and 2 of the national curriculum. But pupils will probably be having too good a time to realise that they are learning as well. Visiting adults have other interests: old chemistry sets, hand-built model cars, magic lanterns and penny arcades where palms are read and personalities assessed can be quite as evocative as any biscuit nibbled in a Proust novel.

Refurbished with Japanese capital, this once-private collection is now open to everyone. The problem of what to do on a rainy or even a fine day in London is solved by this splendid new museum.

The London Toy and Model Museum, 2123 Craven Hill, London W2 3EN Tel: 0171 706 8000. Open every day 10-5.30. Adults Pounds 4.95; children Pounds 2. 95. Group bookings available.