The new BMW M760Li xDrive, the latest in an ever-expanding range of so-called M Performance models developed and engineered by BMW’s M division, that is set to go on sale in the UK later this year, defies classification.

Here is a car that stretches to a limousine-like 5238mm in length. With just about every single feature BMW can muster thrown in for good measure, including standard four-wheel drive and an active rear-wheel steer function, it also tips the scales at a decidedly heavyweight 2180kg. Yet, the leather-lined luxury saloon will storm to 62mph in just 3.7sec, making it not only the fastest accelerating 7 Series model ever produced but, significantly, the fastest-accelerating series production BMW model full stop.

That’s 0.2sec faster than the German car maker quotes for the recently discontinued M5 Competition. It’s also 0.5sec inside the time claimed for its key rival, the more powerful Mercedes-AMG S65. Specify the optional driver’s package, which brings an upgraded ECU governing its top speed, and it adds 34mph to its nominal 155mph top speed to dispatch you to a supercar challenging top speed of 189mph.

The basis for the M760Li’s extreme performance is a heavily reworked version of BMW’s twin-turbocharged 6.6-litre V12 direct injection petrol engine – the N74 as it is known internally. With modified turbochargers and a new fuel injection system that operates at up to 200bar of pressure among a myriad of other changes, it delivers 601bhp at 5500rpm together with a stout 590lb ft from just 1550rpm.

This provides the new BMW M Performance model with 45bhp and 37lb ft more than the older specification version of BMW’s 60-degree V12 petrol engine used by the last generation 760Li. It is also a considerable 157bhp and 111lb ft more than that developed by the twin-turbocharged 4.4-litre V8 petrol engine used by the latest 750Li – up until now the most powerful of the G11 7 Series models.

In the four decades BMW has been producing V12 petrol engines for its series production models, none has been as powerful, nor, I suggest, quite as charismatic.