When the first Mini rolled off the production line in 1959 it was met by a surprised and sceptical public.

Movie-goers knew that Americans drove cars as big as whales - and in that post-war era, the American lifestyle represented progress.

In Britain, however, rationing was still in effect - and then the Suez crisis of 1956 threatened to stem supplies of oil.

Car manufacturers smelled danger - and set their design teams the task of coming up with fuel-efficient automobiles.

With petrol in short supply, the roads had already seen energy-saving bubble cars from Germany.

Sir Alec Issigonis, the brains behind the Morris Minor, was asked by the British Motor Corporation to build a Mini Minor to chase them away. The "minor" was later dropped.

Sir Alec Issigonis: A genius obsessed with space

In just six months, he came up with a revolutionary design where the engine went in sideways - a feature which won the little car worldwide recognition.

Now 40 years on it is acknowledged as both a classic and a national treasure - and has been copied by every small car manufacturer ever since.

One of the first Mini 40th birthday events is a three-month exhibition at London's Design Museum of Mini art cars which include the conceptions of celebrities Kate Moss, David Bowie and Paul Smith.

The location is fitting: the Mini is an ergonomic marvel.

It is small on the outside but big on the inside. It handles like a racing car yet costs a fraction of the price.

John Cutler, a member of the original design team, told BBC News Online: "The designs originated from putting seats on the shop floor.

"Then we got all sorts of people to sit on them - secretaries from the offices, 6ft manual workers - and we got them to indicate what space they needed in the car.

"We measured how much space would be needed to open a map, where a pocket would be needed to stow the map. It is a very ergonomic car."

As a result, more than five million of the little motors have been sold in the past four decades. There are more than 100 Mini owner clubs and countless magazines.

Fashion designer Paul Smith's stripey Mini

And despite adding modern features such as airbags and petrol injection, the Mini remains essentially the same car of 40 years ago.

Issigonis called it "wizardry on wheels", and before his death in 1988, he said: "I thought we had to do something better than the bubble cars.

"I thought we should make a very small car for the housewife that was economical to run with lots of shopping space inside which didn't need a big boot."

Genius on wheels

The result was a car in which 80% of the space was for passengers. It even had hollowed out door pockets and wicker baskets under the seat.

Mr Cutler said: "The principle was to come up with the bare basics for a car, without ostentation, whilst maximising the space available, and making it as fuel-efficient as possible.

"One of Issigonis's peeves about American cars was the thickness of their doors. He used to say that you could build a whole car out of the metal they used for one door.

"He was very insistent that the Mini should have thinner, and therefore lighter, doors."

No overnight success

But despite being nippy, easy to manoeuvre - and cheap at �497 - the car proved to be too much ahead of its time.

A mere 8,000 were sold its first year. It needed BMC's publicity department to give Minis away to celebrities to make the man on the street take notice.

Cliff Richard was one of the lucky celebrities chosen to raise the Mini's profile

It had however found a niche as the solution to London parking and was favoured by the fashion conscious Chelsea set.

Influential 60s fashion designer Mary Quant said of her Mini: "It was my first car and I was very proud of. It was black with black leather seats - a handbag on wheels. Flirty, fun and exciting, it went exactly with the miniskirt."

But, the Mini's real break came in 1961 when the racing car builder John Cooper built his souped-up Mini Cooper.

It was the first British car to win the European Car Championship plus the Monte Carlo Rally three times. And at a street price of �680 the Cooper was a massive hit.

One of the family

A multitude of derivatives followed from luminous vans to the al fresco Mini Moke. The elegant Elf had panache. While the Hornet, with its wood, leather and chrome grills, was in a class of its own.

There have been 28 limited and special editions sporting a variety of exotic names from the Ritz to the Equinox. All too have had special features from leather steering wheels to velvet seats.

The Mini gained in stature with its rally success

The car did not turn into the massive money-spinner which had been expected. It was hugely under priced and very labour intensive - over 3,000 nuts and bolts are in one Mini and all go in manually.

In 1968, BMC became British Leyland which tried unsuccessfully to axe the Mini. Later in 1980 it brought in the hatchback Mini Metro to supplant it.

Nonetheless the Mini continues. And although its current maker Rover is considering its future, it says it will continue making it until 2000 when it launches the new design.

The new model has been described by Chris Rosamond