Road Test: Mercedes-Benz B Class B200 Sport 5dr

Apparently, the new B-Class is the ‘most significantly changed Mercedes-Benz model ever introduced'. A bit of PR puffery, or a coded admission that the outgoing car wasn't up to much? Whatever, the new B is officially a Very Big Deal indeed. Why? Because Merc's new compact car platform underpins it, and will sire not just the new A-Class, but also a mini-SUV, a small coupe and something else that is currently tbc (a cross-over thingy?) There is - quite literally - a lot riding on it.

Proof of this comes in the extravagantly mustachioed form of Daimler-Benz CEO Dr Dieter Zetsche, who has gatecrashed the car's Vienna launch to invite TopGear on a personal test drive and discussion. We're flattered. Dr Z is one of the industry's biggest hitters. German chancellor Angela Merkel is probably never off the blower bemoaning the Eurozone crisis, yet here he is for some TG face-time.

Initially, there are seven different new B-Class models, in various states of trim, powered by two all-new, direct-injection, transversely mounted, turbocharged engines (a 1.6-litre petrol with either 122 or 156bhp, and a 1.8-litre common-rail diesel with 109 or 136bhp). A six-speed manual is standard, and there's the option of a DSG automatic (both also all-new, the double clutch being the correct approach for front-drive Mercs, but not rear-drive, according to Dr Z).

Other top-line highlights include the arrival as standard of another new Mercedes Assist safety system, this time called Collision Prevention Assist (isn't that what the brake pedal is for?). A radar-based set-up which issues visual and audible warnings, it also primes the brakes for maximum attack ("a costly innovation", says the boss, "[which] we compare to the ESP in the first A-Class, and it didn't take a moose to get us there this time").

The chassis, of course, is also all-new, as is the multi-link rear suspension, and the electro-mechanical steering (with its on-demand power assistance, it's part of the B's suite of eco measures alongside start/stop and brake energy recapture). "This is the most significant thing Mercedes has done for some time," the boss reiterates, as we set off.

Is the new B a looker? Not really, but buying a compact people carrier for its shape is like hiring Wayne Rooney to write a thesis on Nietzsche. In silver and on the right wheels, it looks fine, jetting in the body-side crease that enlivens the CLS, and generally looking a lot less apologetic than the outgoing model.

It's also impressively aerodynamic: in full beardy Eco trim, its drag coefficient is 0.24Cd, with 0.26Cd the norm in the range. This emphasis on aero was trendy back in the early Eighties; now, it's all about the quest to reduce emissions and improve efficiency. And it's worked: the B180 CDI with DSG delivers a claimed 64.2mpg and 116g/km of CO2, while the B200 CDI takes things just over the 120g/km barrier.

If you have kids or have ever had a dodgy back, or indeed both, you will appreciate the B-Class's ‘H' (for hip) point. In fact, a decent ‘H' point is one of the reasons you'd get a car like this, and there's something perversely thrilling about effectively walking into a car's cabin. But I also like sitting ‘in' a car, as opposed to ‘on' it, which is where the new B-Class is a huge improvement over the old, mainly because the unusual (and costly) double-floor system has gone, and the seats are mounted 86mm lower. Behind the wheel (the same as you'll find in the CLS, coincidentally), it no longer feels likea small Routemaster bus, either.

In fact, it feels like a compact but substantial Merc: clear dials, premium materials, funky air vents, and the same easy-to-use instrument topography as in bigger Mercs. The multi-media and nav display is now sited in a screen that sits above those air vents doing an uncanny impersonation of an iPad. It's bright and airy, with seemingly infinite headroom, with or without the panoramic roof.

Roomy in the back, too, with seats that can slide backwards and forwards, and fold in the usual bewildering ways, although the middle seat on the rear bench isn't up to much, and with five people on-board, luggage space is squeezed. The new B's packaging is future-proofed, however, for electric and fuel-cell derivatives, which are being worked on right now.

On top of the available SE or Sport designations, the options list is dense with costly possibility: you can choose between Chrome, Sports, Exclusive or Night packages, and much of the available kit has come from bigger, posher Mercs. A £50k B-Class? Insanity, obviously, but a distinct possibility.

It's perfectly nice to drive, especially in punchy B200 CDI Sport form. Although its centre of gravity is lower than before, it's still not that keen on being pushed beyond its comfort zone, a situation the vagaries of the electro-mechanical steering don't do much to help. But that comfort zone is now very comfortable indeed, and it rides sweetly - even on the bigger wheels and firmer Sport suspension settings - and muffles road and wind noise effectively. The pokier diesel is better than the petrol version I tried, simply because of its fatter mid-range torque envelope, and though the new manual 'box is very good, the DSG is better.

Crucially, the whole package vaults the B-Class forward. The old B felt like an afterthought, one of those cars you sensed even Mercedes felt slightly sheepish about. The new one feels just like a big Merc, only smaller. With prices starting at £21,290, the premium Mercedes charges is now at least easier to justify, though we'd still encourage you to shop around. This is a tight segment these days.