Good: strikingly handsome, terrific to drive, surprisingly practical

Not so good: not very full of point

Have we reached peak-niche? The niche-ification of the car market is hardly a new phenomenon. After all, back in the sixties, if you wanted to buy a Mini, BMC would happily sell you the regular Mini saloon, the sporty Cooper, the Countryman mock-tudor estate, the van, the specced-up Riley Elf or Wolseley Hornet versions (with fins!) or even the pickup version. So don't try to tell me that car makers spinning endless variants off of one set of expensive components is anything new, because it simply isn't.

Recently though, what began as a trend has become a full-blown epidemic and things have gone from complex to confusing to flat-out bewildering. Volkswagen can pretty much be blamed for this - in 1998 it spun four separate and diverse models (Golf, Octavia, A3 and Leon) off of a common set of components, spreading the cost of investment and broadening its customer base at a stroke. The rest of the industry took notice, took notes and proceeded to hit copy and paste. Over and over.

With this, the BMW 4 Series Gran Coupé, I think that we may have hit the apogee (or possibly nadir) of niche-ness, the very sine qua non of badge-and-platform engineering. From the same basic box of heavy-metal-Lego that makes up the 4 Series, BMW can also build you a 3 Series Saloon, or Touring estate or GT long-wheelbase hatchback. Or 2 Series Coupé. Or 1 Series hatchback. Or X1 crossover. Or of course, 4 Series Coupé, which is the slinky, two-door version of the 3 Series Saloon.

This 4 Series Gran Coupé then is a four-door fastback coupé version of a two-door coupé version of a four-door saloon, which also comes as an estate and fastback long wheelbase hatchback. Got that? No, and you never will.

This confusion, this apparent desire to build a car not just aimed at a narrow market but virtually at a tiny handful of potential buyers does seem, thankfully, to be coming to an end. MINI has announced plans to row back on the less-well-selling models in its range and other carmakers are nervously eyeing buyer apathy and wondering if perhaps the old days may actually have been good-er. You remember? The days when you chose between a hatchback, a saloon, a coupé, an estate or an off-roader and that was it.

The thing is that it would be so easy to decry and satirise this constant search for more choice, this tail-chasing in the hope of striking a lucrative, previously untapped market. So easy were it not for the fact that the 4 Series Gran Coupé is actually rather a charming and pleasant car, with a modicum of practicality about it.

It actually has the same 2,810mm wheelbase as the two-door 4 Series Coupé, a car justifiably un-famed for its rear seat space. Thankfully, the Gran Coupé has a longer, higher roofline so the rear seatbacks can recline a little more and therefore offer slightly greater comfort. And of course, the extra doors in the back make getting in and out so much easier and more dignified. Still, my eight-year-old son was complaining about a lack of room for knees and feet so make of that what you will.

The boot, accessed by a passably brisk automated tailgate, is decently sized at 480 litres (matching the conventional 3 Series Saloon) and you can increase that to 1,600 litres if you flip the three-way-split rear seats down. Quite why you'd ever do that is unclear (if you regularly carry large loads why didn't you buy the 3 Series Touring or GT?), but it's nice to know that such facility is there.

In the front, the driver sits low and laid-back (albeit at the expense of those in the rear - perhaps my son has a point...) and the quality, layout and aesthetics of the cabin are basically unimpeachable.

As is the tactility and response of the steering. Longer, taller and a little heavier than the two-door 4 Series this may be, but it still reacts and balances on the toes of its suspension like a proper BMW.

Of sheer grunt, there is little enough though. The 418d badge denotes a detuned 2.0-litre diesel engine, boasting (if that's quite the right word...) 143hp and 320Nm of torque. It's adequate but never quite sufficient, and because you have to work it hard to get it going, refinement suffers. Oddly, fuel economy does not seem to and getting the 418d to budge much below 60mpg (4.7 litres/100km) on a long journey or 45mpg (6.3 litres/100km) around town was surprisingly difficult.

The only worry really is that it's all so damned expensive. Fitted out with a few choice options (lovely eight-speed automatic, part-electric seats, spiffy media and navigation system, sexy 19-inch rims and a head-up display for the speedo) our test car clocked in at a hefty €59k. Now, I accept that it is prettier and more rakish to look at than the 3 Series Saloon, but I think I will take that hit in the beauty stakes and pocket €10-20k thanks.

That ultimately is the nail in the coffin. Not so much for the 418d Gran Coupé, which as I said is a lovely thing in isolation, and for a vanishingly narrow customer base might make an ideal purchase. No, more for the whole concept of the thinly sliced niche itself. If you can have more or less the same, for significantly less money, why would you put your hand deeper into your pocket?