This should be the perfect marriage – BMW’s incredibly powerful twin-turbo 3-litre diesel engine and the suave yet practical 6-series coupe. And it does have its appeal: the engine is super-torquey (how does 428lb ft @ 1700rpm sound?) and provides effortless performance, the six-speed automatic gearbox is silky smooth and the interior is beautifully finished. As a place to spend lots of time you can only conclude that the 635d Sport is a mighty impressive car.