Given the average man's choice, the Ford Focus would be near the top of the list: with its amazing agility through twisty stretches, quick steering and subtle rear-wheel steering, it is an impressive piece of kit. But on a road as challenging as the A82, the Focus just isn't quick enough. Which neatly introduces the new BMW M5, which has it in spades. This, the third generation M-powered 5-series, has been under development for three years, which gave the V8-powered 540i the task of toppling the Jaguar XJR and Mercedes E55 AMG, machines at the top of the performance saloon class.
Ever since the first M5 was launched 14 years ago, a special - but very simple recipe - was born. Take a family saloon, cross it with a racing car and the result: the M5. By today's standards, the 24-valve, straight-six 3.5-litre engine packed a relatively 'weedy' 286bhp but it was all hand-built with reinforced suspension, ventilated disc brakes and a limited slip differential. The aptly named M535i created a whole new concept in motoring. By 1988, the second generation M5 had arrived and, despite using the same straight-six engine, by the end of its production its capacity had grown to 3.8 litres, power had jumped to 340bhp and BMW had added its first-ever six-speed manual transmission and computer-controlled adaptive M suspension.
More importantly, this M5 was the first time a series-production saloon had cracked 155mph. Although Jaguar and Mercedes have challenged the concept, one aspect of the M-series remains - image. Minus any extended wheel arches, overblown turbos or spoilers, the M5 has always been subtle to the point of being almost mediocre and it was hard to believe how a car that looked so ordinary was capable of such extraordinary high speeds and cornering forces. But that, in essence, is the beauty of the M5 formula - under-stated power.
And so to the third - and potentially the best - incarnation. On arrival at Glasgow airport, BMW's UK press team gave the car little introduction. There was no laborious Press conference, just the keys and the car.
For this new M-series needs no such prologue. Just digest the statistics. It's the first M car to use a 5.0-litre 32-valve, quad-cam eight-cylinder lightweight aluminium alloy engine - apparently BMW couldn't extract enough power from a six - and a continuously variable double-VANOS timing system which accounts for the engine's astonishing high-revving capability. Consequently, the latest M5 produces 400bhp at 6,600rpm - 40% more than the 540i and 19% more torque at 395lb ft at 3,800rpm.
True to tradition, the new M5 hides its intentions under a discreet shell: re-designed front spoiler with a larger cooling inlet, chrome tailpipes flanking a stainless steel rear apron, massive 18-inch alloy wheels, a tiny rear spoiler and lowered suspension. Inside, BMW has spiced things up with brushed aluminium inserts on the dashboard, gear knob and door inserts and two-tone Nappa leather sport seats. But the pride in M5 ownership comes with the knowledge that, take away the engine and suspension modifications, and you are still left with one of the best executive saloons around.
Wonderfully direct steering gives incredible agility and poise on the road and add the front engine, rear-wheel steering lay-out providing a near 50:50 weight distribution, wide track and long wheelbase makes this one of the most involving executive cars you can buy. On the M5, though, the BMW boffins have added firmer springs and dampers at the front and rear, lowered suspension settings (15mm at the front and 10mm at the rear), compound brakes from the M3, M Roadster and M coupe, the first ever dynamic stability control (DSC) on any M-series car and a limited slip differential to maintain traction even when the DSC is turned off.
Fire up the big V8 for the first time and, at idle, its deep-throated growl sounds delicious. And, from this point on, you know this new M5 means business. Interestingly, there is no red line (probably because it takes a lead-lined right foot to ever reach it), but instead three orange warning lights starting at 4,500rpm and one red from 7,000rpm. From cold, the amber glow is intended to prevent you from over-revving the engine, not that the big V8 won't respond but more a warning from BMW that it strongly advises caution before throwing everything you have at it.
But over-revving this engine is not easy. This unit produces 77% of its maximum torque at idle (1000rpm) and 96% by 2000rpm before peaking at 3800rpm and holding maximum power all the way to 5000rpm. As a result, changing gear is a bonus, but never a necessity. The horizontal torque curve on the new M5 provides prodigious amounts of power whatever gear you're in and, if you don't believe me, check out the figures: 50-70mph takes just 4.8 seconds or 5.9 seconds in fifth.
With such power at your disposal, it's surprising how easy the new M5 is to drive in town. The clutch pedal is not unmanageably heavy, the steering is accurately weighted and it's as docile as a 523i. But it is out of town where the M5 is really comes alive. Acceleration is simply awesome. Whether it is exiting a roundabout or dispatching slower traffic on a fast A-road, you're never in any doubt as to whether there's enough power available or if you're in the right gear. The 0-62mph sprint takes just 5.3 seconds - just 0.1 seconds off the Porsche 911 Carrera 4's pace, equal to the Jaguar XJR and 0.4 seconds faster than the E55; 0-100mph arrives in 11.6 seconds and the M5 tops out at a limited 155mph.
Bare figures alone, though, do little justice to the M5's sheer overtaking ability. The double-VANOS valve timing system breathes extra life into the engine which comes into its own as you climb through the gears and the A82, littered with slow-moving cars, caravans and coaches, provides the right number of obstacles in which to exploit the supercar performance of the M5. With its seamless delivery of power, overtaking isn't a noble art. It's fast, brutal and brilliant.
But while the engine is a genuine masterpiece, the M5 is such a rewarding car to drive because of the superb marriage of every component, not least of which is the ride and steering. The well-balanced ride and exceptional body control that is inherent on lesser models remains and, although the chassis is considerably stiffer, it never becomes harsh or uncompromising. If you want the M5 to be a comfortable long-distance five-seater cruiser, it happily obliges - it's just the other side of its character that brings the biggest smile to your face.
The gear change in any BMW is one of its best assets and the close-ratio six-speeder in the M5 is equally smooth, with an accurate gate that allows you to access the raw power that little bit quicker and easier. The drive-by-wire throttle response is instant with minimal travel but, if you prefer razor-sharp responses, BMW has provided a dash-mounted Sport button. The M5 starts in Comfort mode which is a little misleading: yes, you have to press the throttle a touch harder to extract more performance but it's never lagging in response. Hit the Sport button and the throttle travel sharpens and the steering provides greater feel.
The new M5 rarely gets out of shape even in the wet thanks to the stability control and huge levels of traction from the massive tyres but, in the dry, the smooth power delivery and limited slip differential means it just powers out of even the tightest of twists. Add the accurate steering, balance and grip, and the M5 is a truly incredible machine. As with any other BMW, the M5 is an ergonomic masterpiece with clear, classic dials and faultless build. Standard equipment includes a leather M-spec multi-function steering wheel, electrically-adjustable steering column, digital air conditioning, eight airbags, electrically-adjustable heated sports seats in either Alcantara suede/fabric or two-tone Nappa leather), traction control, ABS and tyre pressure control.
But this wouldn't be a BMW if it didn't have a huge and fantastically expensive options list - and the M5's makes eye-opening reading: GSM telephone (£925), satellite navigation (£3,355 with a 5-inch colour screen). six-disc CD autochanger (£425), electric glass sunroof (£990) and even a climate comfort windscreen (£190).
Just 300 units are coming to the UK this year and, with over 500 orders taken already, you could be in for a long wait. But persevere because the latest M5 is a true work of art. Priced at £59,995 on the road, it may well be out of reach for most drivers, but it's in a league of its own compared to the Jaguar XJR and E55 AMG. The Jaguar is cheaper but the M5's envelope of ability is greater than the Jaguar's and, without the huge and heavy body of the E55, the M possesses greater poise, has sharper responses and is more agile on the road.
But this is letting the competitors off the hook because the true brilliance of this car is its all-round ability. The mighty 400bhp V8 is simply awesome, the ride sublime, the acceleration savage - in fact, my only gripe would be its thirst for fuel: at an average of 20.3mpg, it's definitely not for the shallow-pocketed. But when a car's as good as the new M5 is, who cares?