Audi A3

Specifications:

Model: Audi A3 Cabriolet 2.0 TDI

Price: from £22,750. On sale February

Engine: 1,968cc, four cylinders, 16 valves, turbodiesel; 140bhp at 4,200rpm, 236lb ft at 1,750-2,500rpm

Transmission: six-speed gearbox, front-wheel drive

Performance: 127mph, 0-62 in 9.7sec, 53.3mpg official average; CO2 139g/km

Two things strike you immediately about the new Audi A3 Cabriolet. The first is, what took Audi so long? The current A3 generation has been around nearly five years. The second is that it's a proper soft-top convertible, not a folding-hard-roof coupé-cabriolet as is the current vogue.

Well, openable Audis always have soft tops. As for the timing, Audi launched a lengthened five-door A3 three years ago and now, it says, it's time for the next body shape.

All right, then. Does Audi need another cabriolet? It already has an open A4 and an open TT. But the first is expensive, and the second is almost a sports car and can't carry four adults.

And if you look at this A3 more closely, you'll spot a major innovation of topology. See how long the roof is – how far back it goes? See how short is the top of the bootlid? Here is a stroke of genius. The long space between rear seat and bootlid lets the roof be folded, Z-fashion, into a shallow stack, topped by its rigid front third which makes a separate hood cover unnecessary. That means no unsightly bulge yet a proper boot whose capacity is the same whether the roof is raised or lowered.

It also means the Audi doesn't have the bloated, big-bottomed look seen on all coupé-cabrio- lets. And by placing the hood storage so far back, there's proper rear seat space with sensible legroom and backrests that don't force you to sit bolt upright.

A fabric roof is lighter than a folding metal one, and its folding mechanism can be much simpler. So while you can admire the 25 seconds of mechanical ballet that is a coupé-cabriolet's roof deployment, the mere nine seconds needed to raise or lower the Audi's roof is preferable.

But all Audi A3 cabriolet roofs are not created equal. Grander versions – Sport and, arriving later, S-line – have a fully automatic roof with an extra layer of acoustic insulation, while standard models demand that you clamp or unclamp the front of the hood to/from the windscreen yourself. You can have bright LEDs outlining the headlights, too, acting as Volvo-like daytime running lights, plus various extra pieces of aluminium garnish.

If your first encounter with this new convertible demands accu- rate reversing, you will discover the Audi's worst feature. It may not have the bloated bottom of a coupé-cabriolet, but the tail is still so high, you can see nothing of what lies beneath the parapet. Parking sensors are vital, even more so when the hood is up.

The key test for a convertible, though, is how secure it feels over bumps and ripples. Will it shudder and wobble like an Alfa Spider? Will it feel as though carved from a solid block of granite like a Mercedes SLR Roadster? Or will it be somewhere in between?

The A3 has many reinforcements to compensate for the lack of a permanent roof. There's extra high-strength steel in the windscreen pillars, the sills and the floor, plus a box-like structure between the rear seat's base and the boot. V-shaped braces and aluminium frames front and rear further strengthen the underside.

So does it shudder? It does not. The suspension is set more softly than in other A3s and this helps filter out disturbances that would otherwise tax the body's integ-rity. I began my open A3 encounter with a model whose specification is ideal but not, sadly, offered in the UK. It had the fully automatic, three-layer roof of the upmarket models but the supple suspension of standard versions, plus a new evolution of the VW/Audi 2.0-litre turbodiesel engine.

Why UK buyers who favour the supple springing should be denied the posh roof is hard to understand, but anyway, this proved a very enjoyable Audi, its 140bhp engine now as civilised as a Peugeot/Ford or Renault unit and its suspension able to soak up bumps. The steering is easy, fluid and properly proportional in its responses, and this A3 flows sweetly and accurately through bends with poise and economy.

Next up, an A3 with a new petrol turbo engine of 1.8 litres and a smaller version of the direct-injection unit seen, as a 2.0-litre, in several Volkswagen cars. The 1.8 TFSI produces 160bhp and gives a very different driving experience to the 2.0 TDI turbodiesel. There's still fair pulling power from low speeds but a much broader usable speed range, at the upper end of which the engine stays smooth and sweet. That 62mph (100km/h) can arrive 8.3 seconds after moving off, compared with 9.7 seconds for the TDI, makes the point, but many will prefer the diesel's languid power delivery and far lower CO2 emissions (139g/km against 174).

The most rapid A3 Cabriolet, though, is the 2.0 TFSI, whose 200bhp gives it a 7.4-second time to 62mph. It feels much more muscular than the 1.8 right through the speed range, and its 182g/km average CO2 output is bearable too, given the performance.

There's also a 1.9-litre turbodiesel offered, with 105bhp and a five-speed gearbox. It's the cheapest open A3 at £20,740.

These are proper soft-top convertibles that will match the desires of a great many buyers. Why didn't Audi do it years ago?

The rivals:

Ford Focus CC 2.0 TDCi: from £19,287

Good value in this company but, like the other rivals here, a coupé-cabriolet. Feels great to drive, is best with this diesel. Built in Italy by Pininfarina.

Volkswagen Eos 2.0 TDI: from £21,702

Part-Golf, part-Passat under the skin and a little bigger than an A3. One of the best-looking CCs, good to drive too. Range includes 3.2-litre V6 models.

Vauxhall Astra TwinTop 1.9 CDTi: from £20,465

Looks neater around the tail than the Focus, but boot access is difficult with top down. Can feel a touch wobbly over bumpy roads.