What's all this about?

We've got a new Mercedes-AMG A 45. Or, to be more accurate, we've got four new AMG 45s.

Really?!

Yes, the A 45, CLA 45, A 45 S and CLA 45 S have all been announced by Mercedes-AMG. Every single one develops more than the 381hp of the run-out models of the previous A 45/CLA 45 family, but the top two (denoted by that crafty little S after the vehicle number) feature the most powerful four-cylinder production engine in the world. It's called the M139 in all applications and it delivers up to 421hp.

Never - 421hp?!

Stop with the incredulity. Yes, 421hp. Come on, the 45 had to seriously outstrip the existing A 35 and all its 306hp spin-offs. Anyway, if you go for an A 45 or CLA 45, you'll get 387hp and 480Nm from the 2.0-litre turbo'd four, enough to propel the hatch from 0-62mph in 4.0 seconds precisely and the CLA in 4.1 seconds. Opt for the A 45 S or CLA 45 S, and those outputs rise to 421hp and 500Nm, while the 0-62mph times decrease by a tenth of a second each. As standard, the 45s are limited to 155mph and the S versions 169mph, although you can lift the former cars' limiters to the same as the S models with the AMG Driver's Package option. All the four new 45s gain three-stage AMG Ride Control adaptive dampers, 4Matic+ AWD with a rear torque bias (and a Drift Mode, on the S cars), a new eight-speed AMG Speedshift dual-clutch transmission, an AMG Exhaust, powerful brakes (four-piston callipers in grey on the 387hp models, six-piston red-painted items gripping bigger discs on the 421hp twins) and alloy wheels that are either 18 or 19 inches in diameter.

It looks quite like the A 35 inside and out, doesn't it?

It does, but there are clues as the 45s' potential, if you'd care to look for them. Such as the Panamericana grille with 12 vertical slats at the front, quad exhausts at the rear and a couple of power strakes on the bonnet. Inside, it's all the usual sportiness and MBUX goodness you'd expect of a top-end AMG product, with the 387hp 45s sporting red detailing and the S versions getting yellow highlights instead.