Like the Merc, the two can combine to give a proper kick of low-end torque - as much as 597lb ft, in this case - and improve consumption by up to 15 per cent. As the 750i on which the ActiveHybrid is based manages 25mpg on the combined cycle, we'd imagine that means economy of around 29mpg - hardly revolutionary, but still impressive for a big V8 saloon.

The ActiveHybrid will, as expected, get BMW's stop-start technology already seen on Mini diesels, and lithium ion batteries, which are far more compact and efficient than traditional lead acid units. Still left a touch cold? Well, what about this: we're told that this very drivetrain could find its way into the upcoming 'baby Rolls' saloon.

It's not quite what we were promised hybrids would be like in the future though is it?