I took a phone call the other day from a long-time Mercedes A-class owner. He wanted to know why the brand was deserting just about every value that made his car so ideal for his lifestyle.

The answer could have been delivered direct tonight by Mercedes boss Dieter Zetsche as he unveiled the new A-class. Repeatedly and patiently he explained, "For those that hold the old generation A-class dear we now have the B-class; the new A-class is about something new."

Actually, it's not just about a new car, but a new attitude from Mercedes. So long derided as a maker of cars for old people, this is it's response.

"We want a younger audience to be emotionally attracted to it, not just for the exterior and interior, but also the technology," said Zetsche. "It puts Mercedes on the attack: we expect half of buyers to be new to the brand, we expect the average age to be lower than that of a normal Mercedes buyer and we expect to have more women buyers."

Looking around the three AMG kitted cars on the stage it wasn't hard to understand his point; if it drives well, potential buyers of the Audi A3 and BMW 1-series now have a much harder choice to make, especially if rumours of Mercedes planning a mildly aggressive pricing strategy ring true. Image conscious buyers of a 'VW Golf sized car' end of the market have never had it so good.

Longer-term, though, the question is whether these new Mercedes customers will stick with the brand. For all its qualities, it's hard to imagine the B-class being the next step for anyone who likes their car to have emotional as well as rational appeal, and the C-class saloon doesn't feel like a logical move up the brand either.

Instead, Mercedes will be gambling on their promised three further spin-off models from the A and B-class platform can deliver attractive alternatives. We know sporty, dynamic led SUV is one of the three, and a saloon-like four-door coupe another, but the third remains a mystery.

If Mercedes is to fulfil its growth ambitions, let alone fend off the challenge of Audi and BMW, it had better hope they provide the rungs that keep customers in their showrooms.