So what is it about the Porsche Cayman GTS that is so completely and utterly compelling? Why is it so different to drive from the already very good Cayman S model on which it's based. And is there anything Porsche can do to better it for the rumoured forthcoming R version of its beloved coupé?

The reason it's so compelling, I think, is because it somehow manages to mix such ultra-sharp reactions – be that to its throttle, steering, brake pedal and even its clutch pedal – with a quite extraordinary level of handling forgiveness.

It stops for, turns into and goes around corners with the precision of a competition car, in other words, yet still it manages to feel friendly and approachable and not in the least bit edgy near the limit. And that's a rare if not unique combination for a car that's built to be driven on the road, in my experience.

And then there's the way its engine sounds and responds above 5500rpm, the way its six-speed manual gearbox enables you to slice so cleanly up and down the ratios, the feel and power of its brakes, the clarity and accuracy of its steering, and the near-perfection of its driving position, especially the weighting and location of its brake and accelerator pedals.

Just about everything the Cayman GTS does on the move, in fact, it does beautifully, with an extra 15 per cent more immediacy than in the S version. And that means it feels as sharp and instant as you'd ever really want a road car to, but not so much as a micron more.

Anything more than this and the GTS would feel nervous and neurotic on the road. Yet in the event it goes right up to the point of no return, without going an inch too far. That's how well judged it is as a road car, albeit one that's aimed at the more serious kind of enthusiast.

How can Porsche improve upon the recipe in order to justify sticking an R badge on the tail? I'm honestly not sure it's possible.

As far as I can gather, or certainly according to the rumours doing the rounds at the moment, the next Cayman R might well be powered by a turbocharged four-cylinder engine. That will make it more torquey than the GTS, yes, and appropriately F1 in its technical appeal, for sure. But I can't for the life of me see how a turbocharged Cayman R could get anywhere near matching, let alone bettering, the tactile delights of the GTS.