The powertrain is a force of nature. Driven gently, it could be the most refined of straight sixes; there’s no throb at all because there’s hardly any noise at all. Only when you get going does the character of the engine become obvious, and even then it’s classy and well mannered. There’s more of a rumble when you select the Sport driving regime – which you can do with alacrity because, even though the ride gets stiffer and the steering has a bit more weight, this is fundamentally a long-legged, easy-driving car.
The xDrive system is brilliant at keeping traction: we spent a hilarious 20 minutes trying to get it to break traction meaningfully – and failing. All that traction, when the various stability controls are active, allows the car to put down a great deal of its power without stepping more than a few degrees out of line. It’s fascinating in a car of this power on greasy roads to speculate on just how many bent cars – and lives – these systems must have saved.
The performance is extremely strong – how could it not be, with a 0-60mph time to match many a Ferrari – but there’s nothing explosive about it. That word would imply a lack of controllability, whereas there’s a rationality about the way you drive an M550i even when going pretty quickly. The accelerator has the same precision about it as the steering, gearchange paddles and the pleasantly powerful brakes.
The M550i’s interior contains no surprises. Ours was black, of course, with all the usual BMW controls and decor and a large, panoramic screen dominating things in the centre of the car. The seats are supportive and very well shaped for sporty driving, with a generous range of both height adjustment and fore/aft movement. Rear room is okay without being spectacular for a 5.0m-long car, and the boot space is decent for family holidays.