What is it?
In lieu of the genuine article, the Alpina B5 Biturbo Touring is as close as we will get to a BMW M5 Touring for the current G30 generation.
The B5, which we've already driven in saloon form in the UK, is therefore quite a proposition. In fact, this take on an openly practical 600bhp 5 Series could be even more enticing than a certified M Division ware. The tiny marque's milder, more understated approach to going extremely fast better suits the family car brief, and the 5 Series Touring is the definitive family car.
The build process involves several straightforward but detailed steps. You take the four-wheel-drive chassis of the M550i and with it the 4.4-litre twin-turbocharged petrol V8 originally introduced for the 750i. You then tune the set-up to deliver an ideal blend of performance, comfort and dynamism, the trick being not to focus too heavily on one attribute.
It's this breadth that makes Alpina products so desirable and, at near-enough £100,000 for this particular model, expensive. It's also how you explain the existence of a car that is simultaneously capable of 202mph, has a Comfort Plus mode and could, at a push, fill in for a Ford Transit on moving day.
‘Tune’ is underselling it, really. The B5's front wishbones are entirely redesigned to exact an additional degree of negative camber, improving both steering feel and roadholding. And although the B5 can’t disengage its front driveshafts like an BMW M5, the set-up is programmed to ladle more torque rearwards more of the time – indeed, up to 90% of it.
The steering action is also given a little more meat just off-centre to impart a touch more confidence through 170mph autobahn sweepers. The ZF eight-speed automatic transmission has been strengthened to negate the need for a momentary hiatus in the torque delivery during upshifts. The rear-wheel steering, which uses actuators to angle the contact patch either for low-speed agility or high-speed stability, has been carefully revised. There are shorter, stiffer springs at the front, with wholly bespoke dampers, and the exhaust system benefits from less back pressure.
Alpina finishes things off with an interior trimmed in the same wonderful Lavalina leather chosen by Rolls-Royce. In fact, our test car is conservative relative to what's possible. Visit the factory in Buchloe, Bavaria, and you'll see examples with deeply tanned leather, platted cream piping and wooden inserts so rugged you'd swear they had been ripped off the nearest tree. It's pure Brothers Grimm.