The first rule about the new A-Class is to forget the old A-Class. The previous car, with its slightly dumpy looks, innovative safety-inspired twin-floor construction and unfortunate reputation for instability based on a Swedish journalist failing to keep it rubber side down during a slalom test, shares very little other than its name with this one.The current model is aimed at younger customers who might not previously have thought of associating themselves with the Mercedes-Benz badge. The styling, for example, is as hip as all get out, and I agree with John MacEwan's opinion, expressed in his launch report, that this makes the A-Class more visually appealing than its most obvious rivals, the Audi A3 and BMW 1-Series.But I would also - expanding on other point that John made - suggest that there is a practical cost to this. In achieving the style they wanted, or were asked to provide, the designers have made all the windows too small and all the pillars too large.They have also restricted access to the luggage compartment quite significantly by making the tailgate too narrow and the sill too high. And on top of all that, the A-Class has been created in such a way that you're not going to be able to carry four large adults in it.At six foot three, I can't sit behind the driver's seat when it's positioned to suit me - or, rather, I can, but only if I leave the door open to leave space for my knee, and I don't think any magistrate would look kindly on a car being driven with one door open and parts of me sticking out of it.The interior quality is very impressive, though I didn't appreciate having to lean forward every time I wanted to operate the electronic handbrake switch. The body movement wasn't large, but it was large enough to make me wonder why I was having to arrange myself to suit the car when the car might have been arranged to suit me.On the road, the A-Class suffers from rather vague steering and a suspension set-up which feels as if there wasn't enough time to sort out all the details before the car went on sale - there's almost never a sense that everything has settled down before the next bump, corner or brake application requires attention.The 108bhp 1.5-litre diesel engine is good, though. My only real criticism of it is that if you suddenly ask it to provide power when the turbo is off-boost there's a gap of at least a second before anything happens. But it's very strong in the 1100-1500rpm rev range, which means you can stay in the upper ratios of the six-speed manual gearbox for longer than you might expect.That probably contributes to the official combined fuel economy of 74.3mpg and a CO2 rating of 98g/km which, as you must know by now, shields you from having to pay so much as a penny in Vehicle Excise Duty or the London congestion charge.Running costs should be quite low, therefore, and being in SE manual form this is also the cheapest of the diesel cars in the range, as well as being towards the bottom of the price scale for the A-Class in general. For just over £21,000 you get a decent amount of equipment including air-conditioning, tyre pressure warning, automatic headlights and a lot of safety aids, the most impressive being the pedestrian-protecting active bonnet.More impressive stuff such as Active Park Assist, Blind Spot Assist, cruise control, satellite navigation and DAB digital radio is available, but only if you choose it from the list of optional extras or upgrade beyond the SE specification. Engine 1461cc, 4 cylinders Power 108bhp Transmission 6-speed manual Fuel/CO2 74.3mpg / 98g/km Acceleration 0-62mph: 11.3 seconds Top speed 118mph Price £21,200 Details correct at publication date