Merceds-Benz E55 AMG

Mercedes has its foot on the gas when it comes to developing performance cars. Hot on the heels of the 500bhp S600, the 476bhp E55 also offers comfort, pace and luxury. While UK roads may blunt its charge, the newcomer is an accomplished supersaloon, and a big improvement over its predecessor.

Gentlemen, start your engines! The race to build the ultimate autobahn basher shows no signs of slowing up as Mercedes charges into the fray with its all-new E55 supersaloon.

Offering 476bhp, the AMG-tuned machine is the most powerful production E-Class ever built, capable of sprinting from 0-60mph in 4.7 seconds and achieving a top speed electronically limited to 155mph. Discreetly styled, the E55 relies on a set of 18-inch wheels and a group of four exhaust pipes to distinguish itself from the rest of the range. Hit the throttle, though, and Mercedes' shooting star wastes no time in showing you exactly what it can do. As the revs rise, a mighty 700Nm of torque is channelled through the rear wheels, lifting the nose and making the car squirm.

Aimed at the 400bhp BMW M5 and 450bhp Audi RS6, the E55 hits the UK next month, and is expected to cost from £60,000. Packing a 5.5-litre supercharged V8, it is a huge advance over the machine it replaces. Not only is it much more powerful, but it offers air-suspension for the first time, as well as a new six-speed gearbox.

Technically, the car builds on the strengths of the basic E-Class, which we rate as the finest executive sal-oon money can buy. Interior space is generous, and build quality is first rate. The switchgear is clearly laid out and, although there's no word on equipment levels yet, buyers can expect to find most of the E's options list fitted as standard.

On the road, the car quickly proves that it's an incredibly accomplished mile-muncher. With so much power, cruising over long distances proves relaxing and rewarding. Through long bends, the E55 feels very stable, while the electronic brake set-up offers outstanding stopping ability.

Double-glazed windows, plus more soundproofing than the model it replaces, mean the cabin is quiet at high speed. Indeed, the only sound that accompanies you is the pleasing growl from those four exhausts.

This refinement has its cost, however, and we couldn't help feeling that the steering felt a little vague at the dead-ahead position. The ride is harsh, too, and - despite the versatility of the air-suspension - the Merc struggles to maintain composure on particularly challenging roads. And that steering, combined with the car's size, means drivers will have to work hard in order to maintain the correct line through corners on narrow roads. As a result, it's tougher to drive the E55 quickly than it is the BMW M5.

That noted, the chassis' poise is certain to impress driving enthusiasts, who will love the way in which the car responds to the throttle. Drive hard into a corner, and the E55 understeers gently; switch off the traction control, and oversteer is there on demand.

However, the car's real strength is on the open road, where we think rivals will struggle to match the Merc's incredible power. Forthcoming group tests seem likely to be close calls. Until then, though, Mercedes has definitely given its competitors something to think about...

The fight for class honours continues flat-out!