There are more significant cars at the show, but for Gavin Green, who learnt to drive on a rusty Seventies Alfasud, the new Alfa 156 is the one that brings the biggest smile.

Alfa has been in a bad way for the past few decades. Yet despite the rust, breakdowns, wacky designs, perplexing cabins and general pointlessness of many recent models, there is still a magic about the marque. It is partly the name, so tongue-rollingly romantic, and partly its past. There have been many great old Alfas. Tragically, there have been very few great new ones.

The new 156 promises much more. It looks so lovely, for starters. Not extravagant, not excessive, not particularly eye-catching; rather, like all good design, it has a handsome basic form and caps it with pleasing and imaginative trimmings. The apparent deletion of rear-door handles (they are subtly hidden in a small panel in the corner of the rear window) gives this sporty saloon the look of a coupe, and makes for especially clean flanks. The front-door handles are old-fashioned alloy affairs, redolent of great Alfas of the past yet substantial and pleasing to touch and operate. It also drives beautifully, composed yet brisk, fluent yet with a hint of fury.

The 156 aims to shake up the German makers' dominance of the small sporty saloon market, currently owned by the Audi A4 and BMW 3-series. It is at least as good as these cars, yet more distinctive.

Its excellence should come as no surprise. After all, Alfa really invented the sector, in the Fifties and Sixties, with delicious-looking and driving cars such as Giulias and Giuliettas. They weren't that reliable and they rusted; but few who owned one (and I did) failed to love it. They had such personality and character: such melodious motors, such wholly involving mechanicals (you could almost physically feel the gears meshing). And they were so engaging, on the road, that it was almost as if the four wheels were strapped to your knees and elbows. Your felt very close to the action.

State-owned Alfa, like state-owned BL, lost its way dreadfully in the Seventies. Factories were built to provide jobs rather than to make good new cars. Thus the new Pomigliano factory, near Naples, provided work for unemployed locals from Italy's deprived south. It also served up the worst-made European car of the Seventies, the Alfasud.

My mother owned one and I learnt to drive on it. The interior trim peeled off like the skin of a rotting piece of fruit. And, talking of rot, no car rusted faster. You could almost see, and hear, the decay spreading, so quick was the self-destruction. Our lovely red Alfasud soon turned into a less fetching shade of oxidised orange, bordered by shades of crumbling brown and, soon after, little peek-a-boo holes. Our car quickly became a colander.

Yet it was marvellous to drive! It was engineered in Milan, where Alfas have always come from, and had the most fantastic engine, handling and brakes of its era. But great design is useless if it is badly made. The Alfasud was potentially the greatest car of the Seventies. Instead, it was the most tragic.

The Eighties got off to an equally unpromising start. Remember the Alfa Romeo Arna? It was probably the single most misguided machine of the decade. A joint venture with Nissan, desperate to secure a European manufacturing base in the days before Sunderland, the Arna was a crummy little Nissan Cherry made at the blighted Sud factory. It was the worst possible combination. The world was crying out for an Alfa produced to Japanese standards. Instead, it got a character-free Nissan built in Italy. Nobody bought it.

Yet, unlike BL's sporty saloon brand, Triumph, Alfa has survived. More important, under the protection of a cash-rich and innovative parent, Fiat, it is prospering again. Even the dreaded Pomigliano factory now churns out tightly assembled, quality cars.

The 156 is a Pomigliano product, and while it may not be quite as bulletproof as an Audi A4, it is jolly close. So do go and ogle the 156 at the Earl's Court show. You will not only see a lovely car, you will also be witnessing the rejuvenation of a much-loved marque.