What's it like?
Impressive. On the road the car’s handling gives similarly little away to the coupé, continuing to favour sure-footed stability over the easy-going adjustability you’ll find in an Aston Martin DB11 Volante. It's not the most expressive device, but it corners with a level-headed confidence the likes of which its S-Class compatriot could only dream. In terms of sheer brute thrust, response and efficacy, this twin-turbo V8 must also be among the finest around, even if BMW has resorted to exhaust tuning to give the M850i the character its performance and status warrant.
This car's dynamic repertoire is effortlessly broad, too. On its adaptive, steel-sprung M Sport suspension the ride is firm but pliant and on Spanish roads any vertical movements were decently sympathetic given their limited scope. Air suspension might have pushed the car's personality into a more sophisticated realm, but at what coast? As it is, big body movements are kept doggedly in check – conspicuously well for a two-tonne cabriolet. There’s so much grip and traction that you can then indulge the car’s natural balance and confidently carry big apex speeds without worrying about the size of the thing.
Push too hard and you’ll invite understeer sooner than in the coupé, as the weight tells, though it’s hard to imagine many of these cars being used for much other than GT duties. And duly, with the roof in place, this is a well isolated, cosseting cruiser we’d steer from Portsmouth to Portofino without hesitation and in any weather. Just not, perhaps, if the alternative was a Mercedes S560 Cabriolet, whose motorway ride remains a cut above that of the BMW, and whose interior feels more out of the ordinary.
Meanwhile, with the roof down (allow 15sec at speeds of up to 31mph) and the elegant rear deck exposed, cabin turbulence is quelled very well, and when you’re out among the elements the artificial steering feel also seems less bothersome. Canvas roof stowed away, the 8 Series Convertible is at its best when flowed through corners at no more than eight-tenths commitment, and with short-shifts to lazily ride the beefy torque.
Should I buy one?
Like almost all convertibles, buy one and you’ll sacrifice some practicality – at 350 litres, boot space is 70 litres down on the coupé – while in the case of the M850i also paying roughly £7000 more for the privilege of smelling, as well as watching, the scenery go by.
But in many ways the drop-top 8 Series does have more to recommend it than the coupé, not least because the car’s more benign dynamics better suit the more laid-back cabrio brief. With a continent-crushing range, the diesel could be the star of the range.