What's all this about?

You want a fast Porsche Cayenne these days, you've got lots of choice. To be fair, the entire range is pretty rapid, but there are fast models, and then there are fast models. Starting at the top, the bonkers plug-in hybrid Turbo S E-Hybrid develops the best part of 700hp, although it feels about as heavy as Kenya. To that end, strip out the electrical bits and you're left with the 550hp V8 Turbo, which'd be our favourite third-gen Cayenne if it weren't for the glorious 460hp GTS variant.

This is all very nice, but why are you telling me about the top of the Cayenne tree?

Because there's another, er, high-performance branch about to sprout out of the main trunk. This lightly camouflaged prototype has been spotted pounding the GP circuit of the Hockenheimring (the wonderful old layout was butchered by Tilke, though, and we're still sore about that to this day) in the hands of no less a luminary than Walter Röhrl, two-time World Rally Champion and Porsche Brand Ambassador.

The Cayenne he's driving is said to be a new 'powerful, high-performance' derivative with a focus on 'exceptional on-road performance'. Porsche is being coy about most of the exact specifics but says the hot SUV is undergoing final testing and optimisation as part of the development programme that will see it in global showrooms sooner rather than later. It is based on the Cayenne Turbo Coupe, which leads us to surmise that it can only be a Cayenne Turbo S, presumably with 600hp or thereabouts from an uprated version of the Turbo's 4.0-litre twin-turbo V8. Porsche says it has been designed and developed even more 'single-mindedly to provide the ultimate in terms of longitudinal and lateral dynamics'. To that end, not only is Röhrl putting this über-Caynne through its paces, but test driver Lars Kern is also mucking in too.

Can you really say nothing more than 'it might be a Turbo S' at this stage?

Well, a little bit. There are said to be a host of enhancements for the chassis and control systems, among which the Porsche Dynamic Chassis Control (PDCC) active roll stabilisation has been tweaked to suit this new model, while the front axle is supposedly 'comprehensively revamped'. Kern says: "The PDCC always keeps the body balanced and level even during very spirited cornering. Compared with the Cayenne Turbo Coupe, the front rims are now half an inch wider, and negative camber has been increased by 0.45 degrees in order to provide a larger contact area for the 22-inch sports tyres newly developed especially for this model."

Röhrl, for his part, was impressed by the dynamics, as well as the titanium exhaust system with its pair of centrally positioned tailpipes: "The car remains incredibly stable even in fast corners, and its turn-in behaviour is extremely precise. More than ever, you have the feeling that you are sitting in a compact sports car rather than in a large SUV." He also added that it is a 'great leap forward compared to everything that has gone before - this car redefines the meaning of the team SUV'.

Porsche itself says it is channelling the first Cayenne Turbo S, which had 521hp, and the GTS models stretching right back to 2007 in developing this new variant of the big SUV. We can't wait to give it a try.