4 hundred and twenty one horsepower. Wow. That’s 4 occasions the output of the Mk1 Golf GTI and greater than twice what a Fiesta ST can muster. It’s additionally sufficient to defeat a Ferrari 288 GTO (arguably the primary hypercar) in a sport of High Trumps. The Mercedes-AMG A45 S isn’t only a scorching hatchback. It’s boiling over.

Aufecht, Melcher and Grossaspach (AMG) is a model constructed upon stonking V8s, so the unique 381hp A45, launched in 2013, felt like a chance. But it paid off handsomely, blitzing all-comers in a straight line, doubling its gross sales goal and bringing forth a variety of four-cylinder AMG fashions.

This new A45 S ups the ante once more, headlined by probably the most highly effective manufacturing four-pot engine… (pauses for Clarkson-esque impact) …within the WORLD. Convey it on.

Mercedes-AMG A45 S
(Mercedes-AMG)

Extracting the next particular output than the 8.0-litre W16 in a Bugatti Chiron isn’t merely a case of turning up the enhance. The two.0-litre motor makes use of a curler bearing turbo with an electronically managed wastegate, two-stage gas injection, F1-style Nanoslide cylinder coatings, enlarged exhaust valves, an aluminium crankcase, a baffled sump and separate cooling programs for the cylinder head and block.

Every engine is hand-built in Affalterbach, too – similar to these thunderous and much-loved V8s.

All of it hits the highway by way of an eight-speed twin-clutch gearbox, two limited-slip differentials (mechanical on the entrance, digital on the rear) and four-wheel drive. The end result, in a five-door household hatchback, is 0-62mph in 3.9 seconds. A 288 GTO wouldn’t get shut.

There may be one other startling quantity to course of. At £50,595, or £56,570 for the Plus model pushed right here, the A45 S can also be greater than twice the worth of a Fiesta ST – and enters the realm of ‘correct’ sports activities vehicles, such because the Alpine A110 and Porsche 718 Cayman. For that sort of money, it wants to supply extra than simply pub bragging rights.

Mercedes-AMG A45 S
(Mercedes-AMG)

It definitely appears the half, particularly in fully-loaded Plus spec. The entrance bumper has sprouted a splitter and race car-style flics, whereas the rear arcs right into a brutal diffuser and 4 meaty tailpipes. Solid 19-inch alloys encompass big six-piston brake calipers, painted vivid crimson with black AMG lettering. And a gloss black spoiler is perched atop the tailgate, mentioned to ‘enhance dealing with stability on the bodily limits’.

If all that isn’t unique sufficient, the swoopy Mercedes-AMG CLA saloon and CLA Capturing Brake property supply the identical 421hp firepower with a splash of additional fashion. You’ll pay round £1,500 and £3,000 extra respectively.

Whichever physique fashion you select, you get the identical house and practicality as the usual vehicles. Not like the (equally costly) Renault Megane RS Trophy-R, this isn’t a Nurburgring particular with a chassis brace as an alternative of a rear seat. Its 370-litre boot is on par with a brand new Volkswagen Golf.

Mercedes-AMG A45 S
(Mercedes-AMG)

It speaks volumes for the A-Class that, even on the incorrect aspect of £50,000, you don’t really feel short-changed by its inside. Most surfaces are swathed in supple leather-based or brushed aluminium, garnished with racy yellow highlights and 64-colour ambient lighting (as a result of 63 simply isn’t sufficient). The AMG Efficiency seats look incredible and lock your hips firmly in place, though I’d welcome a bit extra padding.

As beneath the bonnet, there’s a tonne of know-how right here – and getting acclimatised takes time. The dashboard is dominated by two 10.25-inch widescreen shows, configured by way of fiddly touchpads on the steering wheel or between the seats. The graphics are super-sharp and an array of efficiency information is on the market, alongside Apple CarPlay and Android Auto connectivity.

One attention-grabbing characteristic is the AMG Observe Tempo app, which maps out greater than 60 real-world racetracks – together with the Nurburgring – and information your lap occasions, plus full telemetry information. You may even use the head-up show to indicate braking factors, monitor place, the radius of the subsequent bend and extra. It’s the subsequent neatest thing to having your individual pit crew.

Mercedes-AMG A45 S
(Mercedes-AMG)

Previously, big-boosted four-cylinder engines suffered with continual turbo lag, then demanded an oil-change each different month. Not. The A45 S punches laborious all through the rev vary, and its service intervals are yearly or 12,500 miles. It feels unburstable.

Nonetheless, it’s smart to restrict your variety of maximum-attack getaways, if solely in your abdomen’s sake. Choose Race mode by way of the Porsche-style dial on the steering wheel, activate launch management, bury your proper foot and… BLAM! With prompt all-wheel traction, fierce energy and super-quick upshifts by way of the paddles, it squeezes your inside organs so laborious you neglect to breathe.

It sounds nothing like an AMG V8, clearly. However the whooshes, fizzes and pops of this extremely tuned engine – rortier and ruder in Sport and Sport+ driving modes – can’t assist however elevate a smile.

Mercedes-AMG A45 S
(Mercedes-AMG)

So, having lapped the Nurburgring like a professional and embarrassed Ferraris on the site visitors lights, it seems the A45 is fairly nifty on a B-road, too. Certainly, as a way of becoming a member of the cross-country dots, in all seasons and all weathers, few vehicles are so crushingly succesful.

There’s a restrict to how fast you’ll be able to go on Her Majesty’s Freeway, in fact, which is the place the fairly inert Audi RS3 falls quick. But the Mercedes is enjoyable at sane speeds. Its steering is lucid, turn-in is aggressively direct, physique management is unwavering and the brakes really feel mighty. You’re within the thick of the motion, fairly than watching from the sidelines.

The 4Matic+ four-wheel-drive system additionally joins the enjoyable. Just like the now-departed Ford Focus RS, it makes use of torque vectoring to create a rear-biased really feel and successfully quash understeer. Additionally just like the Focus, there’s a controversial Drift mode, which amplifies up this impact by channeling torque to the surface rear wheel.

Both method, that is no tyre-smoking C63 wannabe. My overriding impression was of very good stability and reassuring neutrality. Oh, and pace. So a lot pace.

Mercedes-AMG A45 S
(Mercedes-AMG)

The value paid for such dynamic acuity is a really agency journey, not helped by these unforgiving seats. I might stay with it – and when you’ve learn this far, I think you possibly can as effectively – however it might put me off operating an A45 as a household automotive. A Golf GTI nonetheless does that job higher.

In reality, the A45 S is nearer in spirit to heroes of yesteryear just like the Subaru Impreza Turbo and Mitsubishi Lancer Evolution. It’s a giant-killer, a automotive that makes quick work of, effectively, the whole lot. Even at £56,570, or round £575 a month for the Plus model on PCP finance, it provides an enormous quantity of efficiency per pound.

Above all, it’s a riot to drive. A sports activities automotive such because the Cayman inevitably provides a purer expertise, however if you would like the last word scorching hatchback, look no additional.

Tim Pitt writes for Motoring Analysis

PRICE: £56,570

POWER: 421hp

0-62MPH: 3.9 seconds

TOP SPEED: 168mph

FUEL ECONOMY: 32.8 mpg

CO2 EMISSIONS: 192 g/km