It's fair to assume that the BMW designers tasked with taking the 8 Series, raising its roofline and squeezing in two more doors have had a harder time than most. The bar was set very high indeed by the previous 6 Series Gran Coupe, but you only have to look as far as the 5 Series GT for an example of just how horribly wrong things could go.
Thankfully the four-door 8 Series, which has now been spotted testing partially uncovered in public for the first time, has retained a comparably low-set roofline. To see so much skin on show now is a surprise, with the car not due on roads until Q3 of 2019. But, as you can see in the pictures, the 8 Series Gran Coupe is about 50 per cent identical to the two-door 8 Series.
The bits we can see are all pretty much identical to the coupe that went on sale last month. Only what lies beneath the camouflage is different, where the changes are focused on providing rear passengers with better access and greater headroom. Visible shut lines show that the Gran Coupe will also keep a saloon-style boot opening, rather than going full liftback.
What comes under the bonnet of the more practical 8 will be familiar from the coupe line-up, too. Two variants are due, an M850i and 840d, with the former providing 530hp and the latter claimed to be good for 46.3mpg, so there's a broad mix of abilities to suit most buyers in this segment. For the rest of us, there'll be the M8 in due course. We know a Gran Coupe version of the 600hp plus model is also on its way, having been previewed by the M8 Gran Coupe concept at Geneva in March.
When it arrives sometime next year after the (recently leaked) M8 coupe, the four-door car will, of course, have it its sights set on the AMG GT 4 Door and Porsche Panamera Turbo, which so far has offered an unparalleled mix of performance and practicality in the segment. Time for a change, perhaps?