An engine of this boorish strength gives you licence to disregard the laws of physics, it seems. With a full tank of fuel, our test car weighed in at 2055kg – a touch above the claimed figure but not deceitfully so – and then dispatched 60mph from rest in just 3.7sec.
Moreover, it rattled off the 30-70mph dash in 3.3sec, some 0.2sec quicker than Audi’s considerably lighter but not much less powerful RS4 Avant could manage. The Mercedes-AMG’s engine isn’t quite as flexible, though, taking just under a second longer to dispatch the same increment while locked in fourth gear, but you’ll find keeping the tachometer needle within and indeed extending it beyond the broad 5500-6250rpm window where all 503bhp is metered out to be no chore at all.
Twin-turbocharged it may be, but this 4.0-litre V8 spins freely out to the 7000rpm redline, and how. Indeed, where this car outshines anything else you might reasonably consider a rival – except, perhaps, the Alfa Romeo Stelvio Quadrifoglio – concerns its soundtrack. With the £1000 AMG performance exhaust fitted, there is simply no respite because, even at idle, you get a swollen chug audible from some distance away.