Tom Stewart drives the new BMW M6 Gran Coupe.
 

There really is no other way of kicking off this review without first placing significant emphasis on just how damn fast BMW's M6 is, in this case the sleek 4-door, £94,750 Gran Coupe model. 

In standard form its twin-turbo 4.4-litre V8 motor puts out a whopping 560hp with 680Nm of torque. Needless to say this is substantially more than enough for the car to hit its electronically-limited max of 155mph with consummate ease. It's also good for 0-62mph in just 4.2 seconds.

The version I drove however was equipped with the optional, £5,500 575hp Competition Pack (add £1,000 to that for the M6 Coupe and Convertible models). Despite the extra 15hp, it somewhat mysteriously produces the same 680Nm along with the same quoted performance figures, so you may consider this option a tad extravagant.

In Germany BMW also markets an M Driver's pack for the M6 which raises its top speed to a heady 189mph. However, this isn't an option offered here as it's not UK homologated. 

July saw the introduction of a new 600hp/700Nm Competition Pack for the M6. This costs £6,300 (Gran Coupe) or £7,300 (Coupe and Convertible) and it drops the 0-62 time to a fleeting 3.9 secs, but for a host of reasons these figures - figures which until quite recently were achieved only by a small handful of two-seater supercars - are for the most part immaterial, apart from bar room bragging of course.

In the real world, in this case the A and B-roads of SE Gloucestershire, the 575hp I had on tap was considerably more than required, even for what might normally be considered some quite daring overtaking manoeuvres. Yes, there's power aplenty to very swiftly nip past a slow moving lorry or whatever on a twisting A-road - along with a suitably rousing soundtrack, but if you're picking off a line of vehicles one by one then, such is the immediacy and brutality of the M6's acceleration, you need to be hard on the brakes well before the overtake is completed to avoid slamming into the rear of the next in line. 

Speaking of braking, my M6's optional (£7,395) M carbon ceramic stoppers required only the lightest pressure on the pedal. Any more than that and deceleration becomes almost uncomfortably severe, even when bracing yourself against the steering wheel. 

As you would expect, with 265/35 Michelin rubber on 20-inch M double-spoke alloys, there's more grip, at least in the dry, than you could possibly want on the public road, while the precise steering, uncanny body control and compliant ride all further enhance this maker's fine reputation for rear-wheel-drive excellence. (BMW's all-wheel-drive X-Drive system isn't a 6 Series option.)

For the record, the standard, EU6 emissions compliant M6 Gran Coupe returns 28.5mpg (EU combined) with 231g/km of CO2, although, you guessed, after my test drive the car's trip computer showed a lower figure: 18.5mpg. I reckon 20-25mpg should be the norm on a steady run.

I mentioned the word luxury above, and the M6 Gran Coupe also has that in dollops. My test car's interior (as pictured) was trimmed in a gorgeous 'Sakhir Orange Full Merino Leather', which looks more like red to me, but either way it's a no cost option. The use of leather (with contrast stitching) is now more extensive than on previous models.

Other specification enhancements for 2015 include LED headlamps, a Professional nav system, an impressive multi-functional instrument display and a few other bits n bobs. The latest 6 Series, M6 included, has better connectivity than before with BMW's ConnectedDrive now standard. This provides full nav and infotainment, and the car has its own SIM card - prepaid for UK and European use I might add.

Meanwhile, the list of driving 'systems' grows ever longer. For example, there's Driving Experience Control which reduces exhaust back pressure to enhance the aural experience. There's also Dynamic Damper Control, Adaptive Drive and Integral Active Steering, all of which I'm sure your BMW dealer would be only too pleased to tell you about.

The M6 Gran Coupe is also a mighty good looker. It's sweeping silhouette is very easy on the eye, but thankfully the low, tapering roofline doesn't impinge on rear passenger space too much. The boot's 460-litre capacity is good too, and this extends to 1,265 litres with the rear seatbacks folded. 

So, the M6 Gran Coupe has just about everything going for it - looks, practicality, comfort, luxury, finish and, not least, and in case you're still in any doubt, truly blistering performance.

The only flies in the ointment are its heady price - £106,150 OTR as tested, and the presence of similarly sleek, sumptuous and speedy rivals like the 585hp Merc CLS 63 AMG S and the 560hp Audi RS7. Now there's a tough choice, but to make things easier that's where brand loyalty comes in to play...