The 1964 book of Chitty Chitty Bang Bang, by Ian Fleming has little in common with the 1968 movie.

Now, normally, I'd concentrate on the book, but to be frank, the Disney film is superior in pretty much every way. Fleming wasn't a children's writer, and his Chitty was really not much more than a Q-enhanced James Bond car that led its owners, the Potts family (Father, mother and two children), from place to place, having adventures - it could, fly, swim and track down criminals for Scotland Yard, but overall, it felt pretty tame for children over the age of about seven.

The movie - billed as a "Musical Fantasmagoria" takes the concept a step further, adds a love story, a conspiracy and some dramatic tension - and makes it all so much more fun - possibly not surprising, given that the script was written by Roald Dahl. I'm not saying "don't let kids read the book" - but give it to them before the movie, or they'll be disappointed.

It's the movie that's most loved, so that's what I'll focus on.

Professor Caractacus Potts (Dick Van Dyke) is an inventor - not a successful one, but very, very ingenious. He's widowed, and lives in a windmill littered with devices, along with Grandpa (Lionel Jeffries), and his two children, Jeremy and Jemima (Adrian Hall and Heather Ripley), who, though bright, are running wild, while their father tries to come up with the invention that will solve their money problems. He's a good father though, and the family are as happy as their motherless state and penury will allow them to be.

The children spend their time playing in an old broken-down car in the local garage. When this car is about to be sold and destroyed, they persuade their father to buy it.

Into this situation comes Truly (Sally Anne Howes), daughter of local sweet manufacturer, Lord Scrumptious (James Robertson Justice), first chiding Professor Potts that the children are not in school, and then explaining to him that his latest wonderful invention Toot Sweets (candies with holes that play tunes) are the result of having the sugar too hot.

It's not an auspicious beginning.

The disaster when Potts presents his product to Lord Scrumptious (the sweets attract all the neighbourhood dogs which overrun the factory) wins her sympathy, however. Potts' next moneymaking scheme - a haircut machine - is similarly disastrous, forcing him to flee angry customers, hiding out as part of a carnival show, before sneaking home. After this, he turns all his attention to restoring the car. On the first journey after the car's completion, the family almost literally run into Truly again, and the kids persuade her to join them on a picnic by the sea.

Up until this point, the story is wacky, but still semi-realistic - but from here on, it's pure fantasy as Professor Potts tells a story, centred around the car, Chitty Chitty Bang Bang, which gradually becomes the reality of the movie.

Chitty, it seems, is no ordinary car. It can float and fly, it can drive itself and the evil Vulgarians know about it and want it. They send spies to kidnap the inventor, but mistake Grandpa (who's also Caractacus Potts) for the professor, and whizz him away to Vulgaria, dangling below an airship in his "laboratory" - in fact the windmill's outside toilet.

Potts, Truly and the children set off to rescue Grandpa, but they discover that things are worse than they thought. They find that Vulgaria, ruled by Baron and Baroness Bomburst (Gert Frobe and Anna Quayle), seems to have no children. The local Toy-maker (Benny Hill), who is employed only to make elaborate toys for the Baron, explains that the Baroness hates kids, and to avoid them falling victim to the malevolent child-catcher (brilliantly played by Australian ballet dancer Richard Helpman), the children live a miserable subterranean existence, hidden in tunnels beneath the castle by their parents.

At first, Potts is concerned only to rescue his father and escape, but while he and Truly are off searching for Grandpa, the child-catcher seduces Jeremy and Jemima out of their hiding place at The Toy-maker's and captures them. To save his own children, Potts must save them all.

As a plot is hatched, the Baron and Baroness prepare for bed, on the day before the Baron's birthday, when The Toy-maker's latest work of genius will be revealed. In a delicious comic scene, we discover that the Baron wants his wife dead - they bill and coo endearments to each other, but every time the Baroness' back is turned, her husband tries, unsuccessfully, to do away with her by a variety of means, including trapdoors and an axe.

At the birthday feast, The Toy-maker unveils two life-size dolls: a clown and a singing girl on a musical box, Potts and Truly in disguise. While the court is captivated, the pair let the hidden children into the castle, and the evil adults are netted and imprisoned. Jeremy, Jemima and Grandpa are rescued, and Chitty flies them safely home.

All a story - perhaps.

However, over the course of the day, Potts and Truly have fallen in love, but he can't propose - she's the daughter of the richest man for miles, and he's totally broke. This final hurdle is overcome when Lord Scrumptious announces that he will be marketing Potts' candies - as Woof Sweets - sweets for dogs.

Potts proposes, Truly accepts, and they drive off in Chitty who leaves the ground and flies away in a scene that is echoed and paid reverence to at the end of Grease.

The performances throughout are excellent. Van Dyke learns from his appalling attempts at an accent in Mary Poppins and doesn't even try to sound English, despite the film's setting, which allows us to enjoy his enthusiastic portrayal of Potts without distractions. Lionel Jefferies gives us his standard stalwart character acting to create the eccentric Grandpa, and if the role of Truly doesn't stretch Sally-Anne Howes, she is still sweet and engaging. The children - a solemn pair - are oddly appealing, Benny Hill surprises in a wholly serious role and Gerte Frobe and Anna Quayle as the Bombursts are superbly ham.

The effects, are, of course, dated, but Potts' inventions aren't, because they are real working devices, created by engineer/artist/inventor Rowland Emett. But what really makes the movie are the songs: the bouncy sing-along title track, the haunting lullaby Hushabye Mountain , the energetic song and dance of Me Old Bamboo , the delightful comedy of P.O.S.H, Chu-Chi Face , and The Roses of Success even the somewhat overly sweet Truly Scrumptious and Doll on a Musical Box will have you humming them for days after seeing the movie.

Chitty Chitty Bang Bang has recently been revived as a stage musical at the London Palladium, starring Michael Ball, Emma Jones, Brian Blessed and Richard O'Brien, to rave reviews.