By chance, the last new motoring experience I enjoyed before the Smart Roadster Brabus was at the wheel of a ship-like 1933 Hispano-Suiza J-12 roadster. This was where Pablo Picasso, General Franco and the shah of Persia had once sat, although not at the same time. Hispano-Suizas made Rolls-Royces seem cheap and even lacklustre.

Both smidgenly Smart (not a car, I feel, for revolutionary artists and great dictators) and heroic Hispano are capable of 120mph. But, where the three-ton 1930s roadster required an 11.3-litre V12 engine to run with a force 10 gale, the flea-weight Smart needs nothing more than three cylinders and 698cc.

Size, cost and age aside, the greatest difference in driving these two roadsters is in the way they cover the miles.The Hispano-Suiza enjoys an unrivalled ability to roll effortlessly all day in top gear like some vast motorised leather sofa, while the Smart blips and buzzes, burbles and blurts, nips and tucks its way through city traffic and along wibbly-wobbly country lanes like a hamster in a hurry. And, whereas you would need a crane that can lift a train to carry the Hispano away from an illegal parking bay, the Smart could be picked up and pocketed by a passing toddler.

So dinky is the little roadster, it might just have dropped into the parking space outside your front door from a packet of breakfast cereal. One, or perhaps three, or even five rungs up in terms of performance, safety and comfort from the lilliputian MG Midget or Mini-Marcos of yore, the twin-turbocharged Smart is a clever little devil, although not exactly the kind of roadster you would consider for a London to Sydney rally. I settled for a couple of eventful drives through Ken Livingstone's London APZ (automotive punishment zone), and a lone Saturday morning zip through rutted and rollercoasting Chiltern lanes before anyone else was up.

I suppose two people can fit inside the Smart, but they would be pressed shoulder to shoulder and feel a little claustrophobic with the roof in place. Luckily, this retracts at the press of a button and a yank or two, with various bits of the Smart stored in its tiny see-through boot set above the secret rear-mounted engine. Perhaps these bits, and even bags, can be stowed in the nose of the car, but as I never found out how to open this, I cannot be sure. Whereas you might stow a brace of Louis Vuitton trunks and a few cases of champagne in the footwell of a Hispano-Suiza, a Lucky Bag and a can of Lilt is about all you can squeeze into the Smart.

The French-built, German-tuned Smart Roadster Brabus is undeniably entertaining to drive, not least because, sitting low and stretched out behind its tiny, leather-bound steering wheel, you feel like a budding Le Mans racer. Or a Matchbox version of one. The car is equipped with a Le Mans-style driving kit, including a clutchless, sequential six-speed gearbox operated either by a stubby metal lever or by plastic paddles on either side of the steering wheel. Instead of slotting the gear lever through an H-patterned gate, you simply push it away from you repeatedly to change up, and pull back to change down. And, if this is too much for you, you can slot it into automatic: handy, if hilarious, in city driving. Push your foot down with the transmission in "A" and the little car propels itself forward in fits and starts like a wallaby with a pin in its tail.

In town, the Smart cuts along well enough, although a bicycle would be more comfortable and realistic. At least you can be seen on a bicycle. Minis tower above the Smart, while double-deckers seem like distant mountain ranges. To make sure you don't inadvertently climb the rear face of these, you need to remember that the throttle is where the brake pedal is on most cars: the Smart's pedals are set well to the left. Acceleration is quick enough to get you out of trouble, as long as you keep the revs up and change gear quickly; the brakes are strangely soggy with a long travel, and the power-assisted steering is good, if not nearly so instant or as precise as that of a scythe-like Caterham Seven.

The Smart hustles along the motorway at speed and in tolerable comfort. It whizzes up steep hills with brio and remains stable as it passes coaches and juggernauts. Threading through damp summer Chilterns, it is at its happiest, bucking along, its 17in wheels tramlining under heavy braking along potted surfaces and humping every white line. In this, it is little different from many truly fast sports cars.

Sixty miles an hour seems quick, so here is a car offering all the thrills of more powerful machines, at half the speed, half the space, price and fuel consumption and happily within the law. Well made, but looking too much like a trainer for me, it is, perhaps, a car for the computer-generation motorist. Its computer-activated controls lag in much the same way as TV journalists do reporting from Baghdad. It is not Lotus sharp, but then it is half the price. And, should you ever get tired of its tiny ways, you could always pop it on the back seat of the Hispano-Suiza and use it as a superior form of spare wheel.

· Giles Smith is away.