Porsche 911 Targa

As with its predecessor, the Targa features a full-width glass panel between the A and B-pillars that glides back at the touch of a button to reveal a large opening - ideal for catching a few rays when you're on the move. The transformation from coupé to open-top takes only nine seconds, and once completed there is little in the way of buffeting.

Press a control hidden beside the driver's seat, and the 911 reveals a party trick - a 'hatchback'. Twin gas struts open and close the huge rear window, which is constructed from laminated glass and combines with the transparent roof to provide a virtually uninterrupted view of your surroundings. And in case you're worried about a sunburnt scalp, Porsche has kindly provided an electric sunblind.

As with the roof, the rear hatch can also be opened via a button on the keyfob. So if you don't fancy cramming your weekly shop under the bonnet, you can simply flip the lid and use the 230 litres of baggage space provided with the rear seats folded.

Perhaps the most significant difference between the last-generation car and the new 996 is that it's based on the Carrera 2 coupé rather than the flimsier, less rigid cabriolet shell. The body itself is totally new above the waistline, and incorporates extra strengthening to maintain torsional stiffness. This has added 70kg to the 911's 1,345kg kerbweight and produced a more pointed side window profile at the rear. But the differences on the road are hard to spot - both visually and against the clock.

The Porsche still sprints to 62mph in 5.2 seconds and can crack 177mph courtesy of its 320bhp 3.6-litre flat-six engine. And with the Targa roof slid back, you can savour every crackle, burble and howl from the car's tailpipes in their full, undiluted glory.

Chassis dynamics are also largely unaffected, which means the 911 Targa still steers, stops and slices into bends with a purity of purpose that has yet to be equalled in the field of sports car design. Even better, the rigid chassis displays none of the scuttle shake that afflicted the previous car.

It isn't without its flaws, however. More road noise invades the cabin at motorway speeds than in the coupé, and the view out of the rear window becomes murky and distorted with the roof slid back. There's also the issue of price: a premium of £5,050 over the Carrera 2 is a lot to pay for what is essentially a glorified sunroof.