On any trip to Japan, where I am now, you simply can't miss the ever-present baby cars (known here as kei cars) that line every street and sit shoulder to shoulder in every car park.

The space-saving logic of their boxy proportions, high roofs, straight sides and super-efficient engines is irresistible - but what struck me on this visit (if you forgot the different architecture) was how similar Japan's narrow roads and limited parking places are to many suburban streets in London - where we insist on parking overlong and over-wide saloons, MPVs and estates and are willing to suffer the consequences every morning.

What encouraged these radical thoughts was a brief drive through inner Tokyo in the new Nissan kei car, the funky-sounding Dayz Highway Star. It's the latest boxy creation for this thriving micro car market that collars 40 per cent of car sales in Japan, and rising.

For £6000, taxes paid, you get the 45bhp, non-turbo, three-cylinder, 659cc version of this style-less yet oddly attractive little car; it's just 3.4 metes long but tall and skinny at 1.64m x 1.48m.

And pretty light at 820kg, considering it's a safe and modern structure with the ABS and chassis stability gizmos now considered essential. If you're prepared to invest £8750, you can have a full-house version with a 63bhp turbo engine, climate control, colourful sat-nav, one-shot windows and all the rest.

Here's the point. The Dayz, which has a CVT transmission, is simple fun to drive and has big-car step-off at the lights. It also has surprisingly long legs courtesy of an engine as silent and vibe-free as a Lexus limo.

It steers nicely, grips corners perfectly well on its small-section, low rolling-resistance tyres, and the ride is as good over city ruts (not that there are many in Tokyo) as a decent European city car. And it's much roomier than cars we know with anything like this length and width.

Thus, as you drive, you can't help thinking London thoughts.

The experts say it wouldn't work. There's an interesting piece of YouTube video of a Nissan man from Japan explaining in sign language exactly how fat Westerners wouldn't fit the narrow cabin comfortably (although this fat Westerner fitted quite well). And since kei cars are made only in Japan, every car sold would have to travel 6000 miles from factory to buyer, which would cut its already-meagre earning power.