When BMW branched out into SUVs with the original X5, it was pretty much a no-brainer. Executive saloon buyers were starting to move towards off-roaders and BMW had to be there to meet them.

Having made a success of the X5, the range extended downwards to the X3 and X1 (although one can argue that three off-roaders may be one too many).

However, life then got complicated. BMW was worried that the market was turning against SUVs and wanted an insurance policy.

That insurance policy has recently been launched in the somewhat ungainly shape of the 5 Series Grand Tourer, which is part executive car, part hatchback (up to now those two categories have been mutually exclusive) and part off-roader – oh, and it has frameless door windows in a weird attempt to make it a bit more coupé-like.

The problem with insurance policies is that they seem a bit pointless if you never have to claim on them and SUVs have proved to be far more resilient than feared a couple of years ago – as demonstrated by Jaguar Land Rover announcing a small profit for the last financial year. Thus far, sales of the Grand Tourer have been modest and, unless the concept suddenly catches on, seem likely to remain so.

The Grand Tourer seems to bear out a rule of thumb that says cars that cross two segments might work, but cars that cross three rarely succeed.

The BMW X6 may engender road rage merely for existing, but its premise is clear – a steroidal coupé with 4x4 underpinnings. Many people think the premise is mad, but nearly 2,000 were sold last year, which shows that BMW is on to something.

On the other hand, the Mercedes R Class has badly, and deservedly, flopped. Part MPV, part executive car and part SUV, the R Class is not conspicuously good at anything.
Thus far the 5 Series Grand Tourer seems to have more in common with the R Class (or Vauxhall Insignia for that matter) than with the X6.

Car manufacturers are to be applauded for trying to create new types of car – it takes bravery and a lot of cash, but new concepts do need to answer a straightforward question – what is this car for?

Really successful new ideas are simple: the S-Max is a sporty MPV, the Mercedes CLS is a four door coupé, the very first Range Rover was a luxury SUV.

Like most things in life, if it requires a long and complex explanation, it was probably not such a great idea in the first place.