Porsche, for so long the beacon of exclusive car makers and Europe’s most profitable one, is suddenly looking vulnerable. The bedrock of its recent success, the gargantuan Cayenne SUV, now looks as fashionable as a fur coat; the newly announced Pana-mera appears to be a large and not very attractive saloon about to launch into a market where small has never seemed more beautiful; and even the new 911 has received mixed reviews.

So a lot rests on this latest version of the Cayman. The car is three years old now but has never been a frequent sight on our roads. As a two-seater - but without a convertible roof - it sits in a niche within a niche that has never caught the public’s attention, even though purists and the press have raved about it since it was launched.

Now it is receiving two new engines - a 2.9 litre motor for the standard Cayman and a 3.4 litre for the sporty S model. The suspension, wheels and tyres have been completely revised, while a sharp-shifting, seven-speed, paddle-shift, double-clutch automatic PDK gearbox is also available for those no longer wedded to the idea of a conventional manual box.

More subtle, but no less important to those who will drive their Caymans hard, Porsche is making a limited-slip differential available for the first time. This device improves grip and traction, particularly in bad weather or on the track, and is reputed to have been omitted from the Cayman spec sheet until now only because its inclusion would make the car faster around a circuit than a standard 911 - a bit awkward given the price gulf between them of nearly £20,000.

It is perhaps a sign of the times that Porsche’s press information on the new Cayman cites its better fuel economy before even mentioning its improved performance, but the headline figures for the Cayman S I drove include a 25bhp power hike to 320bhp, a 5.2sec sprint to 62mph (0.2sec faster than before) and a top speed of 172mph - a more modest 1mph hike. If you fit the PDK box, with its launch control system, the 0-62mph time comes down to 4.9sec.

The car as a whole is better than ever. This may come as a surprise, given that the new 911, while technically improved, is a somewhat less desirable and memorable car than its predecessor. The single-minded pursuit of greater efficiency has sucked out and sponged away a chunk of the charm that for the past 45 years has enabled the 911 to stand out from the crowd.

Not so in the Cayman. The new engine does indeed offer better performance and lower fuel consumption than the old unit, but it still sounds great and still responds with joy to every prod of the throttle. Mounted inches behind your head (rather than in the boot, as in the 911), it is a constant, irrepressible presence.

Nor has the car been compromised by Porsche’s modifications to the supension. Since it was launched, the Cayman has always been Porsche’s lightest, most responsive and best handling product, and now its advantage is more stark than ever. And with that trick differential, you can jump on the power at the exit of tight corners, knowing the car now possesses the ability to direct it all where it is needed: straight to the surface of the road.

All that is wrong is the PDK gearbox. Porsche’s official reason for not bringing manual-transmission cars to the launch was that it wanted us to experience the most interesting and exciting variant of the new Cayman range, though I suspect it may have crossed its mind that it would also obviate unwelcome comparison. However, PDK not only saps driver involvement; because Porsche has put the buttons in the wrong place and made them work in the wrong way, it is usually annoying and occasionally infuriating.

The visual changes to the Cayman are minimal and restricted mainly to new front and rear lights, a new front air intake and larger door mirrors. None of this tinkering can alter the fact that the Cayman is a slightly odd-looking beast. Porsche has always been able to work mechanical wonders, but it has been years or even, some might argue, decades since it last produced a truly good-looking car.

Still, no one ever bought a Cayman for its looks. As it lacks the practicality of the four-seater 911 and the pose value of the convertible Boxster, the only real reason for buying a Cayman is that it’s so good to drive, and the good news is that, PDK aside, in this regard it is better than ever.

Do I predict that this good news will result in a sudden boom in Cayman sales? Of course not: even if the current economic climate were less hostile, the Cayman is too narrowly focused on the provision of pure driving pleasure ever to achieve wide-ranging appeal. This is a pity because the Cayman is now the best car in the Porsche portfolio.

Porsche Cayman S
ENGINE 3436cc, six cylinders
POWER 320bhp @ 7200rpm
TORQUE 273 lb ft @ 4750rpm
TRANSMISSION Seven-speed
PDK FUEL / CO2
ACCELERATION 0-62mph: 4.9sec
TOP SPEED 172mph
PRICE £46,069
ROAD TAX BAND F (£210 a year)
VERDICT Porsche’s current best
RELEASE DATE February 21

ALSO WORTH CONSIDERING...

Mercedes-Benz SLK 55 AMG £51,975
For Looks; open top; sweet engine
Against Very dear; not as fun to drive as main rivals

BMW Z4 M Coupé £41,456
For Great looks; smooth engine; good value
Against Cramped cabin; handling doesn’t compare to the Porsche’s