Price: from £21,290
Top speed: 118 mph
0-62mph: 10.4 seconds
Consumption: up to 47.9mpg
CO2 emissions: from 137g/km
Best for: Mercedes' reputation
Also worth considering? Chevrolet Orlando, Ford C-Max, Peugeot 508
The first B-Class, launched in 2005, was perhaps the most disappointing Mercedes ever made. It had its good points, including a roomy, practical people-carrier body and a clever sandwich-floor system. This was designed to provide space for batteries in a possible future electric version and was also supposed to improve crash safety by ensuring that in a heavy frontal impact, the engine and gearbox would be pushed under, rather than into, the passenger compartment. But its drawbacks still outnumbered its advantages; the rough diesel engine and harsh ride were just two characteristics that meant it didn't really feel like a proper Mercedes should.
Now there is a new B-Class, and it has been utterly transformed. While most of the changes have taken place under the skin, even the superficially similar bodywork of the second-generation car sets new standards; painstaking aerodynamic work has given it a drag coefficient of as little as 0.24, an exceptional achievement for a car with such an upright, practical shape. One puzzling difference between the old and new cars is the abandonment of the sandwich-floor system at a time when interest in electric cars is finally beginning to take off. But the fact that the B-Class now sits lower on the road as a result seems to contribute enormously to its greatly improved dynamic behaviour.
There are new petrol and diesel engines – I particularly liked the sweet-running turbocharged petrols – and two new gearboxes; a six-speed manual and a smooth seven-speed self-shifting transmission that uses a dual-clutch set-up similar to Volkswagen's DSG system. Mercedes has also upgraded the interior of the B-Class, but the biggest improvement is in terms of ride comfort, at least if you stick to the standard suspension and the smaller wheel and tyre combinations. It is this change more than any other which at last makes the B feel like a real Mercedes.
Incidentally, none of Mercedes' premium rivals has followed it into the small MPV market. You might think that makes things easier for the B-Class but I suspect the opposite is true. In the absence of comparable models from Audi, BMW, Jaguar and the rest, this Mercedes competes instead with impressive cars of similar configuration from mainstream brands such as Ford, Citroë* and Peugeot, which all sell at lower prices. But the new B-Class is a lot better equipped than the old one to withstand that sort of pressure.