Overview

The Mercedes-AMG A45 S is the pinnacle of the Mercedes-Benz A-Class range. With 421hp, it’s not only the most powerful hot hatch on the market, no series-production four-cylinder engine on sale anywhere provides greater performance. So although at well over £60,000, the A45 S is certainly expensive, you are getting a lot of literal bang for your buck.

There’s only one direct rival: the Audi RS3 Sportback, which at the time of writing is sold out in the UK and not available to order. The 407hp Audi is a little less powerful, but features a five-cylinder engine that arguably adds a little more charisma. Both feature clever all-wheel drive systems for traction and dynamic trickery.

The Mercedes A-Class received a midlife facelift in 2023, but this mostly involved making the standard range look a little more like the AMG models. As such for the A45 S in particular, the only differences about this updated version are new headlights and a change to the badge on the bonnet. This is now the Affalterbach AMG logo, rather than a traditional Mercedes badge.

What’s it like inside?

This is a dividing factor between buyers of this and the RS3, for there will be those who prefer the more traditional layout of the Audi and those who are looking for something much more overtly modern.

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The interior of the Mercedes-AMG A45 S is dominated a pair of conjoined screens that stretch halfway across the top of the dashboard – one for the infotainment, the other for the instrument cluster. Together with the circular vents, yellow accents and user-defined ambient lighting, it’s exceptionally striking, but probably won’t appeal to everyone.

Quality is very good throughout, and Mercedes has paid plenty of attention to the areas you touch a lot – including the air vents and the paddleshifters for the eight-speed dual-clutch transmission. This is a very modern gearbox, and works just fine as a full automatic, but as a driver’s car you’ll also find it gives you an additional layer of involvement whenever you want to take control.

There is an underlying ambience of creakiness about the cabin, which makes you wonder how well it’s going to age. But we’d be prepared to take this risk in exchange for the comprehensively slick MBUX infotainment system – which is pretty to look at and (relatively) easy to get to grips with.

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A final note for the steering wheel: all A45s come with AMG steering wheel buttons. These are housed in their own little pods below the main spokes, and can be customised to activate a number of different functions relating to the way the A45 S drives.

Sounds gimmicky, actually works really well for quickly switching between driving environments (village versus open road, for example). It makes you feel a tiny bit like an F1 driver…

Comfort

AMG fits a great set of sports seats in the front, which manage to be good to look at, comfortable and supportive. We spent an entire day driving this car in a variety of different settings and got out with no feelings of fatigue at all.

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A ‘trendy’ (Mercedes’ word) sage grey upholstery option is available following the mid-life update.

You can get four adults in the A45 (we wouldn’t suggest trying for five – the transmission tunnel for the all-wheel drive system is quite pronounced), but those in the back probably won’t want to be there for too long.

Safety

Being the top-of-the-range A-Class, the A45 S is loaded with standard safety equipment – as well as having a five-star Euro NCAP rating. Though this dates back to 2018, the amount of active safety kit included here would likely make this a top performer even now.

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Highlight features include a pop-up bonnet to reduce pedestrian impact injury, active blind spot assist, active lane keeping and multistage electronic stability control. Somewhat amusingly, Mercedes also lists the AMG Driver’s package as part of the safety and assistance roster, and this actually raises the electronically limited top speed from Mercedes’ typical 155mph to a heady 168mph.

We’d like to point out two other features, though. The Hey Mercedes voice control system, which is better than ever (it can even tell you how to do something via touchscreen if it’s not possible by voice) and the augmented reality sat-nav directions, which can show you exactly where to drive by displaying arrows over a live video feed.

What’s it like to drive?

It’s almost enough to simply say ‘mega’ and leave it at that. This is a comprehensively sorted compact performance car with an absolutely ballistic turn of speed. Yet for all that the speed – which is underlined by 0-62mph in a reliably scant 3.9 seconds – is a major part of the package, it’s telling that it doesn’t dominate the A45 S above all other aspects.

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Rather, everything works in concerted harmony here to deliver very satisfying, very rapid progress when you want it. Or a remarkably relaxed demeanour if you don’t. In spite of its huge power from such small capacity, the engine feels far from highly strung, happy to lope along as if butter wouldn’t melt in its combustion chambers. But if you need to pull the pin and pass slower cars, there are surely few more decisively explosive means of doing so.

Bang, and the traffic’s gone – to the tune of an eager but not over the top under-bonnet cadence and an exhaust system that can do subtle if required, antisocial if that’s your bag. Just be careful going full bore in the manual gearbox mode, since it’s easy to get hung-up at the limiter if you don’t select the next gear in time.

The chassis and suspension cover a similarly broad spectrum of capability. Three-stage adaptive damping comes as standard, and while this – sensibly – never turns the A45 S into a fluffy pillow, it’s compromising enough in its softest setting to allow for comfortable long-distance cruising. Similarly, the hardest won’t take your teeth out – or ruin your date.

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You also get a huge suite of electronic assistance, all operating in tight cooperation with the all-wheel drive system. Turn everything off if you want – or turn it against polite society by activating the built-in, equally tricksy Drift Mode – but honestly it all works so well as intended it’s hard to think of a good reason for doing either of these things.

Direction changes are crisp, the steering more feelsome than Mercedes traditionally bothers with, and the A45 S progresses through hard-driven corners by pushing from the rear rather than pulling from the front – without any real need to get silly about it, this feels great from the driver’s seat.

All told, if there’s not soon a big grin plastered across your chops you’d probably better make an appointment to see about that lack of pulse people keep warning you about.

What models and trims are available?

Mercedes only sells a single variant of the A45 AMG in the UK – the A45 S 4Matic+ Plus (yes, two pluses; one refers to the all-wheel drive, the other to the specification). It comes as a five-door hatchback only, and is extremely well equipped.

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Key elements include the AMG Aerodynamics package, LED headlights, panoramic roof, 19-inch alloy wheels, big AMG brakes (with red calipers), two-zone climate control, 64-colour ambient lighting, keyless entry and start, full MBUX infotainment package, dual 10.25-inch interior screens, 590W Burmester surround sound, and wireless phone charging.

Post-facelift models get more USB ports.

The lesser (306hp) Mercedes-AMG A35 now looks more like the A45 S as standard, but is available as a saloon as well as a hatchback.

Should you buy one? Our verdict on the Mercedes-AMG A45 is on the next page.