When AMG had its wicked way with the SL convertible, it created a phenomenon. The incredible 470bhp 5.4-litre supercharged V8 that AMG and Mercedes developed gave the already fearsomely sophisticated SL virtually supercar performance. Now that drivetrain has found its way into the more graceful CL coupe, which almost three years ago was the first Mercedes to feature 'ABC' suspension and show that a near-two-ton coupe could handle with a level of agility and responsiveness it really oughtn't to (evo 024). Even back then it was no slouch in a straight line, its V8 delivering over 350bhp, but now with the best part of 500 supercharged bhp under its long, sleek bonnet, the CL55 AMG should achieve its full potential.

At more than ΂£93,000 it costs a fraction more than the AMG SL. Value judgements at this level are pretty pointless but with its folding metal roof the SL is both a refined coupe and a convertible, while the CL is only a fixed- head coupe. You do get full four-seat accommodation and a decent boot, though, and from a driving perspective there should be certain benefits that offset the lack of a clever folding roof. Not least of these is more inherent stiffness and a better ride courtesy of the CL's longer wheelbase, although you'd hardly complain the SL was deficient in these areas.

The output of the supercharged V8 has gone up a smidgen since its introduction in the SL55 and now stands at 493bhp, backed up by an immense 516lb ft of torque. As in the SL, this is fed through a five-speed automatic gearbox with three modes - comfort and sport shift patterns in the regular auto operation, plus 'manual' which allows ratios to be selected and held either by nudging the gearlever left and right or via buttons on the back of the steering wheel.
There is an even more potent CL out there already, the CL600 with its twin-turbo V12, so the CL55 needs to be a bit more sporty to justify its place in the range. Visually it does this with five-spoke 19in AMG alloys that are an inch bigger in diameter and wear lower profile tyres, 245/40 up front and slightly wider 275/35s at the rear. The lower body mouldings are also subtly reworked, most noticeably at the front, while four fat tailpipes protrude from the rear apron.

Inside there is a smattering of AMG logos but otherwise the cockpit appears to be the usual CL concoction with almost every surface covered with seamed leather plus a couple of patches of high-gloss wood veneer. Climb aboard, however, and the seat feels quite different, with much more pronounced side bolsters. I'm of average height yet it took me a long time to get comfortable and the seat still wouldn't go as low as I wanted, leaving me feeling a bit cramped in what is a huge car.

The CL weighs a fraction less than the SL55 so you'd expect performance to be of a similar magnitude and it most certainly is. There's a fraction less thunder from the tailpipes but even on part- throttle the CL is startlingly rapid, and with the throttle pinned to the carpet the pace is stunning, punctuated by upshifts that are beautifully smooth and accompanied by an appealing, bassy par-puff as the V8 pauses momentarily. It's worth keeping an eye on the speedo, though: second gear stretches to almost 90mph...

The CL's natural habitat is Continental motorways and fast, sweeping A-roads, though the last CL55 and the SL55 have shown that, with ABC suspension, these big Mercs can handle the cut and thrust of bumpier, twistier tarmac with aplomb. Disappointingly, this particular example didn't, its ride lacking the bump absorption you'd expect, and that's before you've pressed the 'ABC Sport' button which further tightens wheel control. Bigger bumps actually shudder through the body, and that's not all. The thin, large-rimmed steering wheel doesn't feel good in your hands, but worse is the lack of response from the front end when you heft the CL into a decent corner.

With the fantastically accomplished and versatile SL55 on one hand and the more comfort-orientated, mile-munching CL600 on the other, it's difficult to make a convincing case for the CL55.
John Barker