Sebastian Conran's friendly-faced city car is a huge hit in Japan. Guy Bird goes for a ride

The product- or fashion-designer car-collaboration script usually goes like this. Scene one: car company in need of a makeover courts a "hot" product/fashion-designer label to do a "special edition" of one of its ageing motors. Scene two: the product/fashion designer devotes almost no time to the project, sews their logo into the seats, makes a mess, takes the money, and runs. Scene three: the car company now has a dog's dinner it cannot sell and the "hot" designer's credibility becomes lukewarm.

The Nissan Cube Conran Edition is a rare exception. Virtually unknown in Europe, the Cube is regarded by aficionados as one of the most intelligent car designs. It's already a sales smash in Japan, just by being a very well-designed car, based on the Micra platform, which is suited to the city but not lost beyond it.

Its makeover by Sebastian Conran is even better. The son of Habitat's founder, Terence, and brother of the fashion designer Jasper, he has added a tasteful new grille, lights, wheel covers, seats, dash and exterior colour. There is not a single Conran badge in sight, either. With only 5,000 made, it's a genuine rare groove. Conran's own Cube arrived this summer. It's believed to be the only one of its kind in the UK and The Independent was treated to an early spin by Conran himself.

"I used to have a Porsche 911, but it just became frustrating," Conran says as he weaves through traffic. "You've got this big engine, but there's all this performance you can't use."

He traded in the Porsche and, after a year of being car-less, the former car collector plumped for the Cube. It's an unlikely sports car alternative, but its rounded box on wheels offers much more up close. Yes, there is a van-with-windows quality to the Cube. But it also has a great, non-aggressive, round-headlighted "face" and a side-hinged rear door that joins up with the rear side glass to give an uninterrupted wraparound view. This asymmetric look outside is not only unique in the car world, it also offers better vision on the driver's rear offside.

It won't beat a Porsche at the lights, but it's not designed to. It has a frugal, yet perky 1.4-litre petrol engine. Conran says: "I feel completely liberated. It's wonderfully rational, not hung up like a lot of cars are on looking like they do because that's how they've always been; it makes so much blistering common sense."

Despite the plusher feel, it's still affordable, costing about £9,000 in Japan (it sold out in matter of weeks).

In Conran's car, CDs, including the Trainspotting soundtrack and Beethoven, are jammed into the centre armrest; pens and pencils line the glovebox. It is a tidy, but non-precious space. Conran drives calmly, if distractedly, and admits to "letting my mind wander" when behind the wheel, but says it is not as bad as his old tendency for "Braille parking" – that is, by touch.

The worst car accessory he'll admit to owning is a bass driver that was bolted to the floor in his Ford Ka, with no speaker cone. The best one is a 20-year-old A-Z from Smthyson that his wife bought him.

By the end of the drive, I'm keen to buy his Cube, but he's in no mood to sell. "I'm absolutely in love with it. It's everything you get from a big car but you can still get into parking spaces."

And the good news is that the second-generation Cube – due 2009 or so – is set to be sold in the UK and might just get a Conran edition, too. Place your orders early.

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