Engine: Engine 3,386cc, flat-six cylinders, 24 valves, mid-mounted, 295bhp at 6,250rpm, 251lb ft at 4,400-6,000rpm
Transmission: Six-speed gearbox, four-wheel drive
Performance: Top speed 171mph, 0-60 in 5.3sec, 24.6mpg official average
Somewhere near Siena, Italy, I'm discovering just how different the new Porsche Cayman S is from both its siblings. Bend after bend, the new Porsche is revealing its soul: engine howling that Porsche-flat-six howl; steering sensationally lucid; gear-change delicious.
The market positioning may be between Boxster and 911, as is the engine, but the personality is a new direction. So what am I feeling? I'm feeling strong hints of 911, but the Cayman is snappier, easier, and not burdened by a big weight hanging out the back and the need to manage the effect of that weight.
The Cayman feels as I imagine those beautiful 1960s mid-engined Porsche sports-racing cars - the 904 Carrera GTS and its Carrera 6 descendant - might have felt; air-conditioning, sound insulation and four decades of refinement notwithstanding. But not so much refinement as to smother the Porscheness, mind you.
It's a strange thing, but even though today's Porsche engines are water-cooled, they still overlay their intake and exhaust notes with a breathy whine like that of the giant air-cooling fans of old. It's a kind of aural DNA. And talking of genes, the Cayman engine mixes them to great effect.
A Boxster S has a 3.2-litre engine; a 911 engine is of 3.6 or 3.8 litres. So if you mix the cylinder barrels of a 911 with the crankshaft of a Boxster, you arrive at the Cayman's 3.4 litres. The new car also uses the cylinder heads of a 911, complete with VarioCam Plus camshafts, which alter timing and valve lift to let the engine pull hard across a broad speed range.
The result is 295bhp - more than a Boxster, less than a 911. Obviously. So you see that the Cayman does not have a huge number of new and unique parts. In essence, the Cayman is a Boxster with a roof, an addition that makes the structure two-and-a-half times stiffer. And that, in turn, means its suspension can have tauter, sportier settings and the driving experience becomes much more focused.
This pooling of Porsche parts has meant the Cayman was not expensive to develop and it will generate big profits. The new car, by the way, takes its name not from a tax-haven archipelago, but from a type of crocodile. That the initial model has an S suffix suggests there'll be a cheaper, less powerful, non-S at some stage, but even now the Cayman S is significantly cheaper (by £14,450) than the cheapest Porsche 911.
On the face of it, your £43,930 Cayman might seem to be a significantly better buy, as it lacks little for power and pace. Under that long tailgate, moreover, is revealed a generous luggage area to supplement the front 911/Boxster-sized boot. So where's the catch? A 911 has two rear seats, albeit very small ones, while the Cayman is strictly a two-seater, because the engine sits where the rear seats would otherwise be. That makes the engine less than readily accessible, although there's a way into the oil filler via the boot (so don't spill the oil on the carpet). One of the many good things about Porsches is that they aren't very big, so they are much more practical and usable than the wide-bodied exotica that decorate teenage boys' bedroom walls. And for all its obvious Boxster genes, the Cayman is very much its own car with its curvaceous rear wings and neat fastback roof. As with other Porsches, there's a movable rear spoiler, which deploys above 75mph.
You can also raise it by means of a button on the dashboard, thus relieving you of self-incrimination in front of those who might consider it inappropriate for a Cayman S to travel above 70mph. Such souls would be horrified to learn of its 171mph maximum speed and 5.3-second 0-60mph time, even if the fuel thirst is low for such pace. And with that compactness comes the fantastic agility typical of a car with its masses concentrated around the centre. Walter Röhrl, the former rally champion who now works with Porsche's R&D department, says a Cayman is more agile even than a 911.
Conscious of torpedoing Porsche's entire marketing operation, he adds that a 911 has better traction, but the cat is out of the bag. The Cayman is especially good with the optional Porsche Active Suspension Management (PASM), but unlike a 911, it works well enough without it, thanks to a ride that's firm but seldom turbulent. PASM makes the Cayman sit 10mm lower, and in its Sport mode it tautens the damping. Should you also have the Sports Chrono option (complete with stopwatch for timing your hot laps), this mode also sharpens the throttle response. Thus configured, it feels fantastic.
There's one way to spoil your beautifully built, snug and cosy, sensorially spectacular Cayman, though - order it with the five-speed Tiptronic transmission in place of the six-speed manual. Now, with the bigger gaps between the gear ratios, you'll be much more aware of the way the engine's thrustlessens between 3,000 and 3,500rpm, before picking up again ready for the Variocam system's second wind at 4,400rpm. Even worse, the transmission's delayed, uncertain responses to gear-change commands, be they automatically generated or triggered manually by the buttons on the steering wheel, destroy the keenness, immediacy and intimacy that make a manual Cayman S such an intoxicating drive. Avoid the Tiptronic; as I've said before, people who favour that option really shouldn't be driving a Porsche. The indefatigable carbon-ceramic brakes are an option worth considering, though, if you do track days and have an extra £5,349 to spend.
So that's the wonderful Cayman - a remarkable illustration of a rigid, solid-roofed bodyshell's advantages. Compared with its Boxster progenitor, its character has altered completely from satisfying but softish convertible to hard-edged driving machine, to the extent you wonder if you need that expensive 911 after all.
The Cayman S has all the positive Porsche attributes you could want, and none of the snags. It's not the fastest Porsche, not the fiercest, not the most breathtaking. But, overall, I reckon it's the best.
MERCEDES-BENZ SLK 350, £34,930
Metal folding roof stowed, this is a Boxster rival. Raise the roof and it tilts at the Cayman, and you can even have it with an un-Merc-like manual gearbox. Quick, handsome, satisfying but soft-edged.
NOBLE M12, £47,950
Mid-engined like the Cayman, and the closest conceptual rival, Britain's Noble is a thrill to drive and a big success story. Power comes from a turbocharged Ford V6, handling is sublime, detail finish not so good.
TVR SAGARIS, £49,995
TVR blossoms under new ownership and much-improved quality standards, and this is a crazily likeable car: louvres and vents everywhere, 406bhp from the six-cylinder engine, more speed than you'll ever dare use.