What's all this about?

The Porsche Cayenne set new standards for performance in the SUV class when it first appeared in 2002, and now Porsche has launched the ultimate incarnation of its big-selling 4x4. This is the Cayenne Turbo GT, a special flagship model that's offered exclusively in the Cayenne Coupe body style. It comes with a 640hp version of the Cayenne Turbo's 4.0-litre twin-turbo V8 (an increase of 90hp over that model), while Porsche has adjusted the suspension settings, incorporated new dynamic chassis systems and fitted bespoke performance tyres.

Haven't you told us about this car before?

Yes, we reported on the car's progress at the hands of Porsche development driver and rallying legend Walter Röhrl back in May. But this is Porsche's official confirmation of the car and its name. While we predicted the Turbo S badge would be used, we were a little wide of the mark, but hey, we're not psychic, and Turbo GT highlights that this car is a bit special.

For starters, it comes with a load of extra kit that's designed to make it the fastest and best-handling SUV on the market. The big engine is the most powerful V8 built by Porsche, and it has been given a thorough upgrade over the standard Cayenne Turbo's for improved response and to cope with the extra performance. The centre silencer has been deleted, while the exhaust and is made from titanium from there to the tips. We can't wait to hear what the Turbo GT sounds like.

The engine is connected to an upgraded eight-speed Tiptronic S gearbox that delivers faster shifts, while the Porsche Traction Management electronics have been revised and there's extra water cooling for the gearbox transfer case.

This set-up makes the Cayenne Turbo GT fast in a straight line, but a Porsche wouldn't be a Porsche if it didn't corner quickly. The Turbo GT sits 17mm lower than the standard Cayenne Turbo, while the car's air suspension has been stiffened by up to 15 per cent. The Porsche Active Suspension Management (PASM) dampers have been revised, and the Porsche Dynamic Chassis Control (PDCC) system has been tuned in conjunction with a revised front axle and torque vectoring to boost stability and cornering grip. Extra negative camber up front means the bespoke Pirelli P Zero Corsa tyres have a bigger contact patch, while the go-faster updates are complemented by Porsche Ceramic Composite Brakes (PCCB), which are fitted as standard.

It all sounds very impressive, and Porsche proved the car's ability by setting a new lap record for an SUV at the Nürburgring Nordschliefe, with test driver Lars Kern lapping the 'Green Hell' in seven minutes, 38.9 seconds.

Wow, impressive stuff. I guess there's a bespoke look?

There sure is. As well as the coupe-only body style, the Turbo GT features a range of specific design tweaks. Most obvious are the 22-inch GT Design wheels finished in Neodyme silver/gold, while up front there are new air intakes and a redesigned lip spoiler to improve airflow and cooling. There's a carbon roof and black wheelarch extensions, while at the back is a new diffuser, a reprofiled adaptive spoiler and new carbon fibre side plates for the roof-mounted spoiler.

Inside, the car is a strict four-seater, with Alcantara and leather throughout the cabin, while the Alcantara-trimmed steering wheel features yellow stitching at the 12 o'clock position in a nod to Porsche's racing cars. Also new inside is the latest Porsche Communication Management (PCM) system, which makes its debut in the Cayenne range in the Turbo GT. This is version 6.0, which has been seen in other recent new models, and introduces Android Auto smartphone connectivity, alongside the already-fitted Apple CarPlay. PCM 6.0 is now standard across all models in the Cayenne line-up.

When can I buy one?

The Porsche Cayenne Turbo GT is available to order now, starting from £143,910, with first deliveries in the UK due in the autumn. All buyers will be invited to the Porsche Experience Centre at Silverstone to try out their cars and improve their driving skills.