If you're going to drop six figures on a luxury cabriolet, it'll need to be pretty special - there's some incredible machinery at this price point, all vying for that large wad of cash.
Want a luxury long-distance motorway mile-muncher? The Mercedes S-Class Coupe is hard to beat. However, BMW doesn't even see that as a rival, considering its drop-top '8' closer to something like the Aston Martin DB11 Volante. On first impressions, it seems to lack the theatre of the Brit and the opulence of the German - a perfect compromise or missing the mark? That's something only a few hours behind the wheel can answer.
This is the first time BMW has offered an 8 Series Convertible, which is essentially a bigger, more upmarket replacement for the 6 Series. Much like the coupe 8, the convertible is based on the same platform as the 7 Series saloon, which gives you some idea of just how large it is.
Chopping the roof off such a large vehicle runs the risk of creating a chassis that flexes like an overly enthusiastic yoga instructor. However, to keep the body in check, BMW has done some extra welding and reinforcing to add to the 8 Series' already-stiff carbon-fibre core, claiming the convertible is only 2% less stiff than the coupe. Impressive.
Beneath the prominent snout sits a ferocious 4.4-litre, twin-turbocharged V8 engine that makes 523bhp and 750Nm of torque. That's routed to all four wheels through an eight-speed automatic gearbox, with the result being a sub-four-second 0-60mph sprint. That feels brilliantly obscene in such a big, heavy car.
BMW has absolutely nailed a mix of fire-breathing ferocity and silky-smooth responsiveness. Cruising about at normal speeds, the V8 feels refined and happy to sit in the background. But it's always alert, always ready to unleash its inner brute, charging through revs with an angry bark that'd make even the angriest of Doberman hand over its lunch money. The noise-plus-cabrio mix is intoxicating.
Here's where it starts to get complicated. BMW is determined to call the 8 Series Convertible a sports car - more Porsche 911 than S-Class. But it quickly becomes apparent that it can't quite live up to that comparison.
This is a big, heavy car, weighing in at just over two tonnes. To be fair to BMW, it hides it well when you're attacking corners, but it just doesn't show the agility or sharp response you want from a proper sports car. Where it excels, though, is as a GT. Drop the roof and revel in the sound of the V8, cruising in sumptuous comfort surrounded by impressive technology and digital displays - suddenly the 8 Series Convertible starts to come together.
The BMW 8 Series looks about as close to a German interpretation of American muscle car culture as you can get. Up front, there are aggressively styled headlights and angular intakes built into the bumper, while the typical kidney grille has been flipped. The result is a brawny, muscular car that perfectly suits the bark of the V8.
However, the addition of the canvas, electrically folding roof introduces some awkwardness to the profile when in place. It ends earlier on the bootline than the coupe's roof, giving the rear a slightly odd stretched look. Roof down, though, it looks fantastic and perfectly proportioned.
As you'd expect from something that starts in the six-figure price bracket, the 8 Series Convertible's interior is of the highest quality.
BMW falls behind Mercedes-Benz's cabins in this price bracket, but there's a simpler elegance in here that makes the S-Class feel a little OTT, while the latest-generation iDrive infotainment system is as brilliant as ever.
As you'd expect from a 2+2, the rear seats are a token effort - only children could feasibly spend long periods in the back. And if you want to reduce blustering, there's a wind deflector that goes over the top of them, rendering the back unusable anyway. It works brilliantly though, keeping your hair coiffed even at higher speeds.
Meanwhile, the air collar, which blows warm air on your neck from the seat headrest, is standard on all UK cars, making top-down driving bearable even in low temperatures.
The entry-level trim in the UK is M Sport, which includes 20-inch alloy wheels, sporty bodywork extras, an M Sport differential and a sports exhaust system.
Inside, there are leather-trimmed instruments and door panels, a leather steering wheel and velour floor mats. Standard technology includes BMW's assistance and connected packages, which include connected navigation, Apple CarPlay, emergency assistance and other 'intelligent' functions. Laser headlights are a useful option, offering hugely improved visibility at night.
So, we must return to that initial question - does the 8 Series Convertible offer a perfect compromise or miss the mark? To call it a perfect compromise would be to massively overstate matters, but it's close.
Despite its upmarket interior, the S-Class is still just one step better, and while the Aston might look more glamorous, the M850i's shouty V8 manages to push it close for theatre. But if you're looking for a true sports car, it's no match for a Porsche 911.
All things considered, it does manage to find a sweet spot, being capable enough down your favourite windy road to delight, while also making motorway schleps a breeze. And the noise! Did we mention the noise?
Model as tested: BMW M850i Convertible
Engine: 4.4-litre twin-turbo V8
Max speed: 155mph
0-60mph: 3.6 seconds
Emissions (g/km): 161