Mercedes CLA 45 AMG

The CLA 45 AMG is more than just an A45 AMG with sleeker styling and a bigger boot. While it delivers the same earth-shattering pace when required, it's a slightly more subtle take on the AMG philosophy. It's a move that will broaden the CLA's appeal (and is expected to outsell the A45 globally), but the AMG badge has always been reserved for the most unhinged cars on the road. It's a shame then that the CLA doesn't quite deliver the fireworks of its hatchback equivalent, but costs nearly £4,000 more.

If you like the sound of the new Mercedes A45 AMG but prefer something a little more grown up, you're in luck. The newest and smallest member of Mercedes' AMG family has a mechanically-identical twin, based on the CLA four-door coupe.

The CLA 45 AMG use the same 355bhp 2.0-litre turbocharged engine as the A45 (the world's highest output production engine per litre), posts the exact same 0-62mph time of 4.6 seconds and returns identical fuel economy of 40.1mpg. But there are subtle changes under the skin - we learned that the CLA has been designed with marginally softer damper settings and a more subdued exhaust note to give it a more grown up feel.

Well you could have fooled us, because there's nothing sensible about the way the CLA 45 launches itself down the road when you deploy full throttle. Reach for another gear as you close in on the 6,500rpm limiter, and there's a thumping explosion from the exhausts before you're slammed back in your seat again. There was a worry that AMG's first four-cylinder engine wouldn't be worthy of the badge, but it's every bit as brutal as we'd hoped.

Considering the standard CLA's brittle ride, the other concern was that the AMG's suspension (with its stiffer springs, dampers and anti-roll bars) would be back-breaking; and over cracks and speed bumps it is. Build up some speed and find a decent road surface, though, and it flows along nicely, carving from corner to corner with very little body roll and quick reactions.

It was only after we sampled an A45 AMG on the road, fitted with the 'same' performance exhaust as our CLA (and £510 option), and the 'same' stiffer sports suspension (a £765 option) that the subtle differences started to emerge. For starters, crackles and pops on the downshifts, which bring the A 45 to life, have been dialled-out for the CLA. There's also an immediacy to the A 45's turn in which is missing from the CLA - partly due to its 35kg weight advantage, but the different damper settings definitely play a part.

There's plenty to like about the way the CLA drives, though; unlike the Audi S3, BMW M135i and Golf GTI, the steering ratio is constant, which means you need more lock in tight corners, but there's a natural feel when you turn the wheel. The bigger brakes offer mighty stopping power, unless you really give them a work out on track, and the seven-speed twin-clutch gearbox is just as happy slurring along in auto, as it is slamming home full-bore upshifts in manual mode. Our only grumble with the gearbox is a slight delay on downshifts, which occasionally left us in too high a gear on the exit of a corner.

For many, the reasons for choosing the CLA 45 over the A45 will be its bigger boot with the rear seats in place (341 litres versus 470 litres), and the head-turning design. And we have to admit, finished in AMG-specific bodywork with optional 19-inch wheels, it's a stunning thing to behold. But then again the A-Class is hardly a troll, plus the two car's interiors are identical. When you look at it like that, the CLA's predicted premium of £4,000 starts to look steep.