When an interested observer sees the BMW 5-series GT for the first time, it triggers a lot of head scratching. This morning the guy at the car wash – who sees a lot of very smart cars – told me it was the first example he’d seen. He was also trying to get his head around it. ‘It’s sort of like an X6’ was his best attempt.

But I’ve just spent six days in Autocar’s long-term test GT, covering everything from airport duties to a long sprint up to, around, and back from Lancashire. And it makes sense to me.

Read Autocar's BMW 5-series GT reviews

Although it’s a very big car, the raised driving position makes it easy to place and the sense of calm and relaxation delivered by the driving position is quite uncanny. Journeys that I would have normally broken with a 10 minute stop, I demolished in one. BMW really have delivered something truly different in the lightness and airiness of the cabin.

The seats fitted to this car are also something else, As well as the electrically-extendable squabs, the seat back pivots about halfway up, allowing the headrest to right up against your head as well as properly supporting your shoulders.

Unusually, much of what’s really innovative about the 5GT is the experience for the rear passengers. The light cabin, extraordinary view forward and massive (and widely adjustable) rear seat space has to be knocking on the door of what Rolls Royce can offer in terms of rear cabin experience.

There are downsides. This car is also equipped with switchable dampers matched to 20in wheels with very low profile tyres. When the car is started, it defaults to ‘normal’ mode which, combined with these wheels, gives a terrible urban ride. Ironically the ride is much better controlled in ‘Sport’ mode.

Sport mode also allows this big beast to perform with extraordinary élan.

Yesterday I was in the Ribble Valley picking up a pair of speakers (which amazingly slipped into the boot sideways. Dropping the back seats provides a load-through space akin to a ski jump). On the way back to the M6, I took a wrong turning and ended up driving over the fells and through the Forest of Bowland.

The 5GT, despite its size, was easy to drive very briskly and at a decent pace. It also steered into bends with an accuracy and enthusiasm that seemed to be a step ahead of the new 5-series Touring.

Trouble was, I half forgot I had the speakers in the boot. I’ll have to wait until the weekend to see whether they’ve survived the ordeal.