Ruf RT 12

Built by Alois Ruf jnr, whose family firm has been modifying and assembling fast Porsches in Germany since 1948, the car combines the strengthened body of a current 997-generation 911 Carrera with the 3.8-litre bi-turbo from the 996.

The result is a machine which can out-accelerate a Carrera GT, but costs half as much. Admittedly, the ΂£171,000 price is still far from cheap, but few cars match the RT 12 for punch-per-pound.

As well as engine tweaks, the Ruf has a modified bodyshell, with a new nose and imposing carbon fibre rear wing. It rides millimetres from the tarmac, while Pirelli P Zero tyres and huge air intakes front and rear make it obvious at first sight that this is no 'ordinary' Porsche.

Inside, drilled aluminium pedals and carbon fibre details set the cabin apart, while you have to negotiate a custom roll cage to get in. On the road, the stiffened suspension causes the car to weave over uneven surfaces. Yet with so much steering feedback, it feels stable. And it needs to be, as the twin turbos respond instantly to throttle inputs, giving ferocious pace.

Yet as the Ruf is so capable, you never feel anything but totally confident in its abilities - so it's surprisingly relaxing to drive. Also, the 650bhp engine happily runs at low speeds, and the suspension can be adjusted automatically, lifting the car to clear speed bumps and potholes.

Far from being just another modified 911, the RT 12 is as carefully developed as any official performance special. But as Ruf's history dates back to Porsche's beginnings, we'd expect nothing else.