As we've said before, the E55 has the ability to hide its monstrous performance particularly well. While we had the car, passengers often commented they'd no idea they were travelling in one of the world's fastest estate cars - it takes a determined prod on the accelerator to switch from cruiser to bruiser. Once the supercharger does get to work, though, the E55 is truly, devastatingly quick.

Inside, only the cheap-looking silver dials give the game away that this isn't any other E-class wagon. There are plenty of clues on the outside, though, with four enormous tailpipes poking out from the rear valance, drilled, ventilated discs clamped by multi-piston callipers and badges everywhere shouting AMG or V8 Kompressor, depending on where you're looking.

On the move the E55 boasts a better ride than the RS6 and a more informative helm than the rather sullen Audi's. Use the performance and the traction control becomes a busy bunny, even in the dry. Turn it off and be prepared to be quick with the opposite lock; two of the evo team had nasty moments in the E55 when it suddenly snatched back just as they though it was all under control.

And how does the Audi shape up? A massive part of the RS6's appeal is in the way it wears it performance on its sleeve. From the moment that twin-turbo V8 engine grumbles into life it leaves its occupants in no doubt what this car is all about. On the facia, where the E55 has a clock the RS6 has an oil temperature gauge. The slightly lumpy ride (courtesy of lowered suspension and massive tyres) also tells you this car means business. And although it wears only a couple of discreet badges, everyone can spot an RS6 from a thousand paces.

The RS6 might not beat the E55 against the clock but it always feels quicker and will win any traffic light grand prix thanks to its four-wheel drive and instant grunt. So what if the Merc's quicker from 120-140mph? I'd rather have a car that can use all of its explosive power overtaking a dawdling lorry, like I have to do every day.

The E55 Estate is a fantastic car but the RS6 is an even better one. The Audi is the Real Deal, something special, something classy and characterful. Mercedes keeps getting close to greatness but never quite close enough.