The world's most winsome car accessory? No arguments about this, I would suggest. It's the circular metal stencil of a flower that you can get to fit over the brake lights of a VW Beetle. (This is not an official VW accessory, I should stress. You get them from independent car-trimmers and Beetle fan sites.) Once in place, this unique device ensures that your braking action appears to the car behind you not as a solid warning light, but as a display of loveable red petals.

It's the winner, no? At any rate, it's hard to think how you could get your car to be more cuddly, short of actually re-moulding its entire body in the shape of Snoopy.

True, as another road user, it might be scant consolation to you that the last thing you saw, as you hurtled helplessly towards a sudden build-up of traffic on a wet motorway, was a pair of luminous daisies. But anything that keeps the still valuable message of flower power alive is good, I guess.

Some have argued that the modern, four- seater take on the old German lovebug was already pushing the boundaries of cute to the point where only people with the strongest stomachs for ironically consumed kitsch needed to apply. This, don't forget, was the car that came with a dash-mounted flower vase - a slim, clear tube, suitable for a single stem. And that was an official VW accessory. One waited for other manufacturers to respond to this bold horticultural development with bigger, better vases of their own, creating a kind of nuclear vase race - Vauxhall coming back with a dash-mounted flower jug, Citroën upping the ante still further with a huge glass orb, Honda topping them all by introducing a pair of stout, ceramic outdoor planters, one on each wing.

It didn't happen, though. Maybe, in the end, people are less keen to invite the garden into the car than VW imagined. Still, the flower holder is still there in the new upgraded model, but if you want to make your brake lights look like flowers, then I reckon you might have a problem. The brake clusters are now bigger and more elliptical (one of the larger adjustments in what is otherwise a fairly minimal cosmetic nip and tuck job), and my hunch is that a stencil overlay won't produce the same effect. Ah, well. As they say: you winsome, you lose some.

Overall, though, does this redesign signal a new seriousness for the widely loved Beetle - a plan to look earnest and urban rather than like something in which a girl might keep her pyjamas? I might not be best placed to answer this question because the one I borrowed for a week was bright yellow.

I've got nothing against yellow in itself. It works perfectly well on bananas and I wouldn't want custard to be any other colour. It also has an important part to play in children's paintings of the sun, not to mention a critical role in the world of the high-visibility tabard and similar items of potentially life-saving fluorescent clothing. It's only when it's mashed up and spread all over cars that I wonder about the wisdom of it.

Don't think you can escape the paint job by climbing inside the Beetle, either. The colour creeps up over the window sills and slides down the insides of the doors to a depth of about 6in. During some mild moments of paranoia in the Beetle, I began to suspect that the colour was still advancing under its own motion, creeping ever onwards, and that soon everything in the car, including me, would be banana yellow, permanently.

Still, if you can put the paint job behind you, there is no denying the unusual quantities of good feeling the car generates - both in you, chuckling away behind the wheel, and in the other drivers you encounter, who appear to feel only warmth towards the Beetle and the motives of its driver.

The VW designers seem to have come up with the perfect passive shape. You could drive this car really nastily - cutting into people's paths, slamming yourself right up against people's rear bumpers, flashing, honking, and with someone exposing their backside in the rear window, just for good measure - and no one would even see you doing it. They would just see one of those friendly Beetles, and smile indulgently.

That's the magic of it. This car doesn't just discourage bad road behaviour, it actively absorbs and eliminates it. It's a force for peace, with or without the flowery add-ons.

Volkswagen Beetle Luna 1.6

Top speed: 111mph

Acceleration: 0-62 in 11.6 seconds

Average consumption: 37.7mpg

CO2 emissions: 180g/km

Eco rating: 6/10

One careful owner: Alicia Silverstone

On the stereo: Ne-Yo

In the glovebox: plant food

Bound for: Monte Carlo

Buy it because: Herbie lives

Marks out of 10: 7

Price: £12,635