It might not look very different in the pictures but in fact this car represents radical change, and over the coming months we'll see the introduction of a raft of new variations on the Arnage. The Arnage T is the first to arrive and will be the flagship of the new range, boasting the most powerful version of the classic Bentley V8 engine we've yet seen.

Bentley has modified the engine extensively, firstly to help it comply with ever more stringent emissions laws around the world and, secondly, to give a further chunk of horsepower to the already healthy total. The engineers have done this by replacing the previous single turbo with a completely new twin-turbo system that allows closer coupling of the catalysts to the cylinder heads so they can heat up more quickly. The fun side-effect being that the twin Garrett T3 turbos spool up way quicker than the sole oversized T4 of the previous set-up, giving a radically different feel to the engine and its responses.

The new engine retains the familiar 6.75-litre capacity but now churns out 450bhp at 4000rpm and 645lb ft at 3250rpm. Compare that with the Red Label's 400bhp at 4000rpm and 619lb ft at 2150rpm and you can see how the twin turbos have added more action higher up the rev range. Bentley has also raised the rev limiter by 500rpm, so the action now continues until the giddy heights of 5000rpm.

The engine modifications don't stop there either because the heads are revised with improved gas-flow around the new, lighter valves, while the exhaust manifolds are fabricated tubular types, rather than the old-fashioned cast iron variety fitted before.

Bentley is very proud of the fact that the engine is now controlled by the Bosch Motronic ME 7 ECU, which features fly-by-wire throttle control, permitting the development of a new ESP stability system, replacing the rather crude traction control set-up of the Red Label.

There are subtle changes to the rest of the car, too, including extra bracing in the roof and sills, stiffening the body by 10 per cent. The spring rates are increased front and rear and the car gets a rear anti-roll bar for the first time, which, together with a stiffened front bar, helps increase the roll stiffness by 57 per cent over the Red Label. For the first time Bentley has made a 19in wheel and tyre combination available, which enhances the chassis mods.

Look hard and you can see the boot lid profile has changed slightly with the introduction of an integral boot spoiler that does nothing to improve the slightly old-fashioned appearance of the Arnage from the rear. The front is a lot smarter though, with larger scoops in the air dam to help feed cooling air to the front radiators and the bigger front brakes.

The interior mods are less successful. The dash now sports a turned aluminum surround for the dials, fitted over the existing wood veneer. To my eyes it doesn't work but apparently the Americans don't like the all-aluminum look so this is the unfortunate halfway- house result. Meanwhile the new gear selector looks as if it was stolen from the Harrods toy department and should really be swapped for the previous item before anyone notices, but at least all the cabin metalwork is beautifully milled, then sumptuously chromed.

My first go in the car turned out to be around the inner circuit at Rockingham. It's a tight, twisty ribbon of tarmac that doesn't have a straight worthy of the description, yet the speed at which we approached the first corner came as a shock. This is a seriously big car to hustle round a circuit. The power is certainly there, those turbos spooling up much quicker than before, punching hard up to 2500rpm then getting a second wind past 3000rpm that'll catch you out if you're not careful. Still, it was nice to test the ESP so early on in the drive... Unfortunately the brakes haven't been changed and still have that strange Bentley feel with no discernable biting point and a brake pedal that never actually goes solid underfoot. You can press it to the floor if you try hard enough, yet with 348mm ventilated discs up front and 345mm versions at the rear the actual power available is immense. It's just hard to modulate them with the current set-up. At least the chassis seems up to the challenge and offers a marked improvement over the previous car, although ride quality suffers with the 19-inch wheels fitted.

Performance is astonishing with 60 available in 5.5sec and 100mph in 13.5 (compared with 15.5 for the Red Label). Bentley has limited the top speed to 170mph although its masters at Audi always like to make the most of the five per cent allowable tolerance, so expect this car to sail past that figure in style.

The current feeling at Bentley is that its cars should always have excessive power available and it has certainly managed that. I never thought it would be possible to over-engine a two-and-a-half-tonne car, but that was before I'd tried the Arnage T. It sets a new benchmark amongst deranged super- saloons that will be very hard to beat.