BMW is facelifting its most controversial model, the X6. And what better way of tidying up this coupe-cum-SUV than adding a diesel M version?

The new X6 M50d is among the first of a new range of stop-gap M models to slot between the full M GmbH cars and the trim-level M Sport models. It'll sit alongside the new BMW M550d xDrive also unveiled today.

It has a new upgraded version of the same 3.0-litre straight six TwinPower turbodiesel, with greater boost from three turbochargers to deliver 376bhp and a monstrous-sounding 546lb ft of torque.
It's the most powerful diesel BMW has ever built.

It's the most powerful diesel BMW has ever built. 

So the new BMW X6 M50d (2012) is quick, right?
Oh yes. This is another fast four-by-four to spark fierce debate in chartrooms up and down the land. It hits 62mph in 5.3 seconds - enough to embarrass many Porsches.
BMW defends such high-riding lunacy by pointing out that the new X6 M50d also averages 36.7mpg and CO2 emissions stand at 204g/km. 

And what's all this about the X6 being facelifted?
BMW has indeed refreshed the X6. As you'd expect from any of Germany's premium car manufacturers, this is a modest facelift. Any untoward blinking, and you may indeed miss it.
The chrome grille is a little wider and the detail bars are new; the foglamps are repositioned; active LED headlamps are now available; out the back, you'll find a rear lamp cluster with subtly different graphics and those now-trademark horizontal light bars that make the latest 5-series so distinctive at nighttime.
It's not all cosmetic. Much of the front-end tidy-up in fact improves engine cooling and breathing, while new flaps beneath the front apron are designed to boost stability.
  
And if the X6 M50d isn't fast enough, can I still waste my money on an X6 M?
Naturally. If you've got a spare £85,680 lying down the back of the sofa for an X6 M. The new super-diesel SUV-coupe-thing X6 M50d costs considerably less at £62,260, landing in UK dealerships on 16 June 2012.
You can order the same spec X5 M50d for a couple of grand less; it wears a price tag of £60,325 and has the same breathed-upon 3.0-litre twin-turbodiesel.