Not so long ago, in an office far far away, the Mercedes board decided that perhaps cost-no-object development budgets weren't quite the right way to satisfy shareholders. So the engineers suddenly had to economise.
Unfortunately, one of the side effects of limiting development budgets was a slip in quality. Something had to be done and a new boss was appointed to smarten up the small-car affiliate and put a little spit and polish back into the dulled three-point star.
The consequence of having budgets capped was to do what everyone else in the industry does, and get stuck in to some platform-sharing, so suddenly we have a whole new Mercedes clan including the new B-Class, which is an A-class off-shoot.
Simplistically, the 'B' is an 'A' with a stretched platform and body, the wheelbase up by 210mm and overall length by 432mm. Larger motors help to overcome the average 185kg rise in excess weight. Mercedes describes the B-class as a 'sports-tourer', of which there are three versions.
Full review here