If pushed to nominate the greatest year ever for supercars, 2004 would have to be in the reckoning. It would probably need to fend off 1985, when the Lamborghini Countach QV went head to head with the Ferrari Testarossa but the almost concurrent launches of the Porsche Carrera GT, the Ferrari Enzo and the Mercedes-Benz SLR McLaren took quite some topping. The problem is that with manufacturers desperate to one-up each other with ever more outlandish 'halo' products, standing still in this market is going backwards. Hence the launch of the 722 version of the McMerc.

Let's put the need for this car in perspective. The standard McLaren Mercedes Vision SLR cost £317,565, developed 626bhp and would rocket to 60mph in 3.6 seconds on the way to a top speed of 208mph. Back in 2004, this was enough to open a clear gulf between this class of car and the more mass market supercars. Thing is, it's no longer enough. Take the Lamborghini Murcielago LP640 as a for instance.

Here's a car that features a 640bhp V12 that will fire it to 60mph in 3.3 seconds (0.4 seconds faster than the previous model), with a top speed of 210mph and which not only wears an arguably more charismatic badge but also charges its customers a mere £190,000 for the privilege. Did I mention it's also four-wheel-drive? Cars like this and the genre-warping Bugatti Veyron indicate why McLaren and Mercedes needed to breathe on the SLR a little.

The result is the SLR McLaren 722 edition. No, that's not the amount of power this car churns out although that would be welcome. Instead the 722 generates a healthy 650bhp and also features more than 300 modified components. For Mercedes-Benz, "SLR 722 edition" was an obvious name for the new model variant, as it evokes memories of the unforgettable victory achieved in 1955 by the British motor-racing legend Stirling Moss and his co-pilot Denis Jenkinson at Mille Miglia, at the wheel of a Mercedes-Benz 300 SLR with the start number 722 (indicating a starting time of 07.22 hours).

"If you want a supercar with presenc,e there is arguably none better at dropping jaws than this SLR 722 edition"

Driving the Mille Miglia route puts Moss' achievements into perspective. Gaping drop-offs, scabby surfaces, claustrophobic villages and mile upon mile of twisting and turning hill routes make an average speed of 50mph seem adventurous. Back in'55, driving on unyielding crossplies and with no seat belts or disc brakes, Moss set out at 7:22 in the morning and covered 1,000 miles, returning sooty and exhausted at 5:40 that afternoon, logging an average speed of just a fraction under 100 miles per hour. The 722 is a fitting tribute to this remarkable achievement from the greatest driver never to win the Formula One world title.

It'll certainly have exclusivity on its side with only 150 models being produced. Not that the standard SLR is a common or garden sight. I don't think I've ever seen a private example on the road. When you do chance upon the SLR on a motor show stand, the dimensions of the thing seem cartoonish, extreme and resolutely head-swivelling. It's almost as if somebody had morphed an SL into a massively priapic silhouette.

Up front is a hand-built 5.5-litre V8 supercharged engine. Actually up front may be something of a misnomer as the engine's weight sits behind the line of the front axle, making the car (in modern terms) 'front mid-engined'. Weight distribution has long been a pet obsession of Gordon Murray, the McLaren man largely responsible for the iconic F1 hypercar, and the SLR offers exemplary balance. In case you were wondering what occupies the space in front of the engine under that lengthy bonnet, there are a pair of carbon fibre cones fully two feet long that are designed to disintegrate in the event of a head on collision, thus dissipating the shock loading.

The 650bhp engine will fire the SLR 722 edition to 60mph in 3.4 seconds, and to 124mph (200km/h) in just 10.2 seconds. Top speed is a heady 209mph. Although the numbers themselves may be impressive and stand comparison with rivals like the Porsche Carrera GT and the Ferrari Enzo, the SLR is cut from very different cloth. It's cloth that includes climate-controlled air-conditioning, an automatic gearbox, a superb CD stereo system that feeds seven Bose speakers. Satellite navigation, electric seats and an electrically-adjustable steering column? Check. Tyre pressure monitors, automatic headlamps and front, knee, head and thorax airbags also feature. Although 44kg has been pared from the weight of the 722 edition with more carbon fibre and lighter 19-inch alloys it still weighs in at a hefty 1,724kg. A bare bones Le Mans version would be even more devastatingly accelerative.

The cabin is supremely well finished, as you'd expect when paying this sort of money, but it is small. Once ensconced, the engine is started by flipping back the top of the gear knob to reveal a starter button. It's only when the car is given its head that it all starts to make sense. Even at 100mph, the car is shrugging in disdain, pitying your sorry attempts to discover its raison d'etre. Find the right roads or tracks where speeds in excess of 150mph are possible and everything gels, the engine finally capable of showing what devastating shove it has, the aerodynamics gluing the SLR to the bitumen. Quite how many customer cars will ever be driven in this fashion is open to debate but make no mistake, the McLaren in the genes is the real deal. This is no badge engineering exercise.

The Mercedes-Benz SLR McLaren 722 edition is a breathtaking achievement but one that merely adds a footnote to an astonishing chapter in supercar development. The McMerc project was always too compromised, too riven with internal bickering to produce a truly cohesive end result but there can be no denying this car's presence. Even an Enzo pales beside it. Despite its quirks, it's probably the most special of all the hypercars.