After all, says the designer of the revamped vehicle, the power-to-weight ratio enabled him to sail past Porsches on the bends at the Fuji Speedway racing track, as he put the prototype through its paces.

"When Caterham first offered me this job, in 2006, I said that we should make a 'kei car' because it would be perfect for the Japanese market," says Justin Gardiner, brand director for Caterham Cars Japan.

"I have been saying that firms like Rover, MG and Lotus should have been doing [this] for 20 years now."

A kei car is defined by the Japanese government as having a maximum engine displacement of less than 660 cubic centimetres and being within strict restrictions on its size. In return, the vehicle excise tax, the car weight tax and the annual road tax are levied at lower rates, while there is no need to guarantee off-road parking in much of Japan and insurance is also significantly reduced.

Those savings make this class so popular with Japanese consumers that more than 40 per cent of all the vehicles sold in Japan carry the yellow plates that mark them out as a kei car. Similar breaks are available in other regions. In Hong Kong, for example, motorists who buy a new car that is on the government's list of "environmentally-friendly petrol private cars" can enjoy savings up to HK$75,000 on the first registration tax.

And with other major cities examining similar schemes to reduce pollution, there is a lot to be said for keeping a kei car.

All these factors support Gardiner's belief that the new working relationship with Suzuki - which has experience with kei cars and builds the best-selling Wagon-R series - has so much potential.

"For Caterham, this is very much a case of us going back to our roots, when we made the car as light as possible and put a small engine it," Gardiner says. "And I am certain that it will sell in this market."

Founded by Graham Nearn in 1973, the company's Caterham Seven is a direct evolution of the Series 3 Lotus Seven that was designed by Colin Chapman. The car earned a reputation among enthusiasts as one of the most iconic sports cars of the 20th century.

In April 2011, Tony Fernandes, the owner of AirAsia and Queens Park Rangers Football Club, added the car company to his portfolio.

With the support of both Caterham and Suzuki, Gardiner worked with renowned engineer Aki Musashino - who learned his skills in garages in the East End of London and now restores Formula 1 racing cars - to develop the new car.

While the instantly recognisable body of the Caterham Seven remains, the new car has been fitted with a Suzuki 660cc engine, which Gardiner has been able to coax more than 150km/h out of.

Similarly, the gearbox, axles, differential and rear brakes are all from a Suzuki van and are being shipped from Hamamatsu Port, near the firm's Shizuoka headquarters, to Caterham's factory in Dartford, Kent.

Development was done under the strictest secrecy over two years - although a Japanese magazine came close to letting the cat out of the bag after one of its journalists spotted Gardiner testing a prototype at the Fuji Speedway track.

Fortunately, the magazine leapt to the wrong conclusions and reported that the Caterham-Suzuki alliance was to build a new version of the Suzuki Cappuccino, a two-door roadster that was popular but only in production for seven years from 1991.

Gardiner admits the Cappuccino was a major influence on the development of the new Seven. He bought several of the cars at auction to disassemble them and work out the engineering challenges ahead of him.

"From the outside, the car looks the same as any Caterham," says Gardiner, who salvaged engines, gearboxes, axles and other components for the first prototype.

"The difference is that the regular version weighs 550kg, but this one is down to 400kg."

It was that power-to-weight ratio that enabled him to muscle past Porsches on the bends at Fuji, although Gardiner admits the German cars' power enabled them to catch him up on the straights. The braking and handling of his prototype are "marvellous", he adds.

"The size of the vehicle is completely appropriate for Japan and its speed enables it to dart through the traffic," he says.

"The Germans and Italians do love to drive fast on the motorways of Europe, but the dedicated Japanese driver prefers to test himself on the tight roads of the mountains," he says.

"That is the mark of a driver in Japan, because any fool can go fast in a straight line. And that means this Caterham is perfectly designed for Japan."

The kei Caterham will be available for order from October, priced at about 3 million yen (HK$234,938), and Gardiner is anticipating being able to double his present monthly sales figure of five cars.