Describe the seminal Porsche 911 and it would have to be the entry level rear-wheel drive Carrera coupe. It's the truest expression of the 911's brand values and the car with the purest bloodline back to the original 901 concept. Some customers aren't so hung up on historical rectitude, however, and just want a car that's right for them: a car with unassailable grip levels and an open top without running the 911's silhouette for instance. The idealists can have their Carrera 2 coupes. Pragmatists, on the other hand, shouldn't score the 911 Targa 4 from their shortlists.

The old '996' series Targa was never offered in all-wheel drive form, Porsche mothering a little in diverting from the classic 911 template. Perhaps this was due to the already groundbreaking change from air cooling to liquid cooling that version of the 911 underwent, Porsche possibly wanting to keep other changes modest in order to salve the diehards. With the cooling now a non-issue, and the Cayman model line starting to come into its own, Weissach now feels a little more freedom to tweak the 911 range a little, hence the wacky colour schemes of the GT3 RS, the divergent detailing of the Turbo and the introduction of the Targa 4.

The glass roof keeps the 911s characteristic shape intact, although the car loses the elegant Bezier curve of the rear side window - that shape being replaced by an acute angle that is probably the Targa's most distinctive external signature. A polished, anodised aluminium trim strip runs along the length of the roof frame. The glass roof gives the interior an airy feel and opens in no fewer than seven seconds to as much as half a metre. The great thing about this is that, unlike with a convertible, the operation can be done on the fly at any road speed. The roof itself is constructed of two-ply tinted glass which weighs 1.9kg less than the Targa roof in the 996 generation 911. A revised sealing system boosts refinement at speed and a wind deflector minimises annoying turbulence. There's a lot of glazing above your head and if you just want the air conditioning to do its thing without blowing a gasket, a black internal roller blind provides shade, operated by a rocker switch next to the handbrake.

"The Targa4 is aimed at the atypical 911 buyer"

It's easy to forget that, unlike other 911 variants, this car actually features a hatchback which offers 230 litres of space with the rear seats folded, making this the 911 to have if you plan on two-up touring. The tailgate can be released via a door-mounted switch or by the key fob. There's even electronic assistance to help close it if you have an armful of gear.

These days, the Porsche Targa packs a 3.6-litre engine good for a punchy 325bhp, with the 3.8-litre S variant we're looking at here packing 355bhp. The S version is certainly the one to go for and Porsche's sales figures to date appear to back this up with most customers plumping for the more powerful car. It's easy to see why as soon as you turn the key. The distillation of disparate orchestra pieces into a pure Porsche sound is backed up by some fiendishly clever engineering in the shape of Porsche's Variocam system - a variable inlet-timing system that gives a more useable spread of torque across the rev range.

This increased flexibility is the first thing that seasoned 911 drivers will notice when driving the latest model, making the engine feel as brawny as a decent V8. When the 911 went water-cooled in 1997, many thought a great engine had been adulterated, but they were missing out. The liquid cooled engines were better than ever and driving them back to back with a 1995 model 911 Carrera 4 just highlights how much more muscular they feel. Expect 60mph to come and go in 4.6 seconds, and Porsche claim exemption from the 'limited to 155mph' brigade by letting the 911 run on to 179mph.

If you can't stretch to the S variant, the 3.6-litre model is no slouch, however, jetting to 60mph in just 5 seconds and on to a top speed of 174mph. Quite how effective the wind deflector is at these sorts of ballistic velocities can only be guessed at. The six-speed gearbox is one of the best in the business, although if you really want to go out on a limb away from the 911 mainstream, you could specify the optional Tiptronic S five-speed automatic which features gear changing rocker switches on the steering wheel.

Although it looks ostensibly similar in profile to its predecessor, the 997 generation Targa has lost those turbo-look smeared-on headlamps and also receives different bumpers front and rear plus twin ovoid tailpipes replacing the previous car's smaller round items. Keen spotters will notice improved seats and higher-grade plastics used throughout the cabin. Lucky owners will now benefit from a passenger glove compartment, Turbo-style instruments and the attractive three-spoke steering wheel that previously only resided on Porsche's astonishing options list.

Some 44m wider at the rear than a two-wheel drive 911 variant, the Targa uses much the same bodyshell as a 911 Carrera 4/4S with the same Visco multi-plate clutch system marshalling the traction duties. This can dole between 5 and 40 per cent of drive to the front axle which means that the Targa, despite its 4wd tag, retains a healthy rear-wheel drive bias at all times.

Porsche has fitted the car with its Vehicle Tracking System. A pocket sized card should be carried when the car is in motion. If the car is moved without the card being present or if the car senses itself being lifted or towed, a tracking system is activated and using GPS technology, is able to trace the vehicle.

Though prices kick off at £70,320 for the Targa 4, the Targa 4S we're looking at costs £77,370. In other words, Porsche has deliberately positioned this car so that it's no longer seen as the poor man's 911. Far from it. Compromise may be a dirty word to some 911 anoraks but Targa owners are cut from different cloth.