What is it?
This is the biggest-hitting variation of BMW’s ungainly 6 Series Gran Turimso. As such, it's an intriguing proposition, even if it is unlikely to rack up vast sales figures here in Europe, back-seat loving China being the main target market for a class of car that also includes the Mercedes-Benz CLS and Audi A7 Sportback.
We’ve covered the 6 Series GT in considerable depth before – not least by way of a full road test – but this is our first experience of the 640i on home soil. Because the chances of a M-division Gran Turismo are slim to non-existent, it's this model that tops the line-up, with a 335bhp twin-turbo straight-six petrol engine nesteld longitudinally under the bonnet.
Beneath it in the range sits a limited selection of powerplants. And don’t be fooled by BMW’s model taxonomy – the 630i that serves as an entry point is now a four-cylinder petrol turbocharged to develop 255bhp (not a six-cylinder, as the '3' would historically have suggested). The solitary diesel option comes in the form of a turbocharged straight-six tuned to 261bhp and 457lb ft of torque.
While the 640i also comes exclusively with BMW's full-time four-wheel-drive system – xDrive – you've got options with the suspension setup. As standard, the Grant Turismo is fitted with self-levelling air suspension at the rear axle. Adaptive suspension costs £1670 and adds air suspension to the front axle; for your money the dampers will also now be adaptive, meaning the ride height can be dropped 10mm in Sport mode.