Under the bonnet is where the technical improvements for the B4 S over the B4 end, though: Alpina has stuck with the same suspension settings, meaning it sits on slightly less aggressive springs and dampers than its cousin from BMW's M division.
As before, the B4 S gets BMW Professional infotainment as standard, which adds a widescreen sat-nav and all-round parking sensors. The car’s seats also come wrapped in Dakota leather at no extra cost, although the car you see here features Merino leather, a £1285 option.
What's it like?
Very approachable. From the press of the starter button to the first prod of the throttle in Sport mode, the B4 S is a docile beast. Where the M4 awakens with a deep-throated growl, the Alpina, blowing through its standard-fit Akrapovič exhaust, has a subtler, softer voice.
Leave the drivetrain set to its default Comfort mode and the only hint of its potential performance comes with the effortless way it shifts the car’s 1690kg mass. The engine barely treads over 2000rpm during normal urban driving and the gearbox flicks into seventh and eighth surprisingly often.
The benefit of the N55 lump’s Alpina modifications becomes clearest when it’s set to Sport mode and allowed to spin towards the redline. The engine is responsive from low down the rev band and there’s a very obvious kick at 3000rpm that’s accompanied by a silky in-line six-tone. On upshifts, there's a hefty shove in forward thrust.
Even with its more accelerative powertrain, the Alpina is better than the M4 in placing that power onto the tarmac. Where the M4’s grunt lands in one explosive strike that almost always seems to overcome the grip on offer, the Alpina’s more elastic motor transmits its power onto the ground with a rising surge. This means you can drive with more confidence than one does in the edgier M4 and it allows you to be more aggressive with the throttle on corner exits.
That’s not to say that the B4 S is faster than its BMW sibling. The M4, with its hunkered down body and significant weight advantage, turns and stops faster. But the Alpina’s less hard-edged suspension irons out creases and cracks in the road more effectively - impressive given that the car sits on big 20in Alpina Classic alloys. It makes maintaining a smooth pace along a B-road much easier and doesn’t require the wide-eyed focus of the M4 on a slippery surface.
Combine this with wonderfully consistent steering that feels perfectly weighted to a car with this much muscle, plus a highly responsive gearbox that can be controlled manually via Alpina’s shift buttons on the back of the wheel, and you have a car that is as flattering as it is rewarding to drive.