To celebrate 25 years of the M5, BMW have built a special one-off custom, “the M5 CSL we never built” according to Albert Biermann, head of BMW’s M division. With a heavily modified version of the award winning V10 – stroked to 5.5l, fitted with a carbon fiber intake and a secondary oil cooler this beast produces 580hp – an increase of 76hp over the stock model. To keep the power in check a new version of the 7 speed dual-clutch box fitted to the M3 has been fitted. Add a carbon fiber roof to lower the centre of gravity, lightweight carbon fiber seats and rip out the rear seats and the car has shed over 50 kilos. The upshot is that the M5 CSL lops a whopping 20 seconds off the stock car’s Nürburgring lap time.

While it is a tour de force technologically sadly we will never be able to buy this car – it is strictly a one off and with all the compromises – what is the point of the world’s fastest four-door saloon if there aren’t any back seats? – it’s probably for the best. If you want a track day special, an M5 isn’t going to be it.