This is the new BMW 3-Series Gran Turismo, a longer, taller, hatchbacked version of BMW's compact hero that's perfect for... erm, actually we're not quite sure what the 3 GT is perfect for. Truth is, we're struggling to figure out quite what it brings to a world already containing the most excellent 3-Series saloon and Touring.

So help us, please. We shall furnish you with the 3 GT's vital stats, and then you shall explain its grand purpose in life. No pressure.

You'll remember BMW has previous in this department: in 2009 it released the rather unloved BMW 5-Series GT. That car was important for us because it previewed the excellent chassis of the (then) new 5-Series. So what's this one all about?

Well, BMW wants you to think of it as an "elegant business carriage and a dynamic, comfortable tourer". The proportions certainly look better resolved than they did in the 5 GT. A low benchmark, admittedly. It's 200mm longer and 81mm taller than the BMW 3-Series Touring, with an automatically opening and closing hatchback that offers up 25-litres of extra storage space than that estate.

It also gets an active rear spoiler, which we're told is the first of its kind on a Beemer, reducing lift at ‘touring speeds' (this is BMW-speak for ‘hellish-fast'). An active spoiler on a hatchback BMW? There's a sentence we never thought we'd say. The extra length in the wheelbase (110mm) of this GT over the 3-Series Touring means rear passengers benefit from increased legroom, while it's even easier to get into thanks to seats that are higher than the standard car. The Pensioner's BMW?

Perhaps. Assuming The Pensioner enjoys a turbocharged 3.0-litre straight-six petrol engine with 306bhp and 295lb ft of torque, because that's what you get in the range-topping 335i Gran Turismo. As such, it'll go from 0-62mph in 5.7 seconds and hit a limited top speed of 155mph. Other, more wallet-friendly variants are available of course: there's a 328i and 320i petrol, along with 320d and 318d diesel engines, the latter of which returns 62.8mpg and emits 119g/km of CO2.

You get a six-speed manual as standard, though an eight-speed auto is available as an option, and underneath, it's the same as a regular 3-Series, but with a bias towards "directional stability and long-distance comfort". Motorway schlepping, then. You can of course, spec the M-Sport pack, which lowers the car by 10mm and offers up stiffer springs and dampers and anti-roll bars, along with 18/19in wheels.

There's lot of other eco gubbins too, such as brake energy regeneration, start/stop and an ‘eco pro' mode that works with the sat nav, monitors your driving style and suggests the most fuel efficient route. Top Gear does not understand this setting.

Prices will be announced in due course, but for now, TopGear.com, pray tell us: what the bloody hell is the 3 GT for?