This new, fifth-generation M5 reverts to a V8 and conforms (slightly) to today's downsizing mantra by having its pistons displace 4.4 litres instead off the V10's 5.0. Yet power rises, from 507bhp to 560, and torque even more so: 502lb ft are now on tap, all the way from 1500rpm to 5750. The engine is actually similar to that found in M-badged versions of the X5 and monstrous X6, with the two twin-scroll turbos nestling in the vee and each turbo's two exhaust entry pipes fed from opposing banks for the most even turbine-driving pulses, but the Valvetronic cylinder heads are new. So instead of an M-car's usual throttle per cylinder, we now have no throttles at all. It's all done by varying the valve lift. CO2 output has plummeted, incidentally: 232g/km against 357.
Along with the plumpest torque curve ever found in an M5 comes a new, seven-speed, double-clutch gearbox in place of the old and surge-prone SMC paddle-shifter. Now you choose from three shift-speeds instead of six, and you have direct button-access to three levels of sportification for engine response, steering response and damper firmness. Two 'M' buttons on the steering wheel can remember two sets of favorite settings.
So, has the M5 gone impure on us? It has not. With all controls in their gentlest settings, it feels like a very fast, regular 5-series. Set to Sport Plus, it's monstrously rapid (0-62mph in 4.4 sec, max 190mph) and has the torque spread to punch gloriously out of bends. Peak power plateaus-out at 6000-7000rpm, but 4000rpm is usually plenty. There's a deep, gutteral boom from within, at high revs an almost flat-crank blare (thanks to the turbo plumbing) from without.
It rides firmly but sensibly, the steering gets crisper as you move off centre. Best, though, is the fantastic throttle-steerability encouraged by a differential which actively directs torque to the rear wheel with more grip rather than braking the one with less.
Go hard into a bend and the M5 understeers. Now, instead of easing off, you apply more power and the back scribes a wider line. Perfectly-metered, progressive power oversteer whenever you want it, and it's wonderful. The price? £73,040.