Four years ago, when Vauxhall began work on designing and building the new Insignia, the market wanted family cars that were stylish, safe, quiet and comfortable. And if that meant they also weighed as much as a small hotel, nobody was too bothered. That’s why even the lightest Insignia weighs more than 1.5 tonnes — some 10% more than the Vectra it replaces. Unsurprisingly, it also uses more fuel, pumps out more CO2, has slower acceleration and a lower top speed. They call this progress.

There is increasing public apathy towards this bread-and-butter type of car. Why drive a staid saloon or humdrum hatch when, to cut a dash, you can have an Audi or a BMW for the same money? Maybe you’d be better off in a recreational SUV, or, if it’s a properly practical car you need, why not buy a seven-seat MPV for the price?

The dice seem loaded against the Insignia from the start — the wrong car for the wrong time. So it’s a surprise to discover how well it fares in spite of hostile market conditions. Vauxhall rightly decided to bin the old Vectra name, and while Insignia sounds pretentious, it at least comes unburdened by the Vectra’s inseparable association with dire depreciation.

And it’s an all-new design from the tyres up, which looks — dare I say it — terrific, and even better in the flesh than it appears on this page. Sleek, curvaceous and cleverly proportioned, it’s taller than the old Vectra, yet looks as low as a coupé. Smarter still is an interior that offers decent seating for up to five, despite that raked roofline.

The Insignia will be here by the end of the year, wearing both hatchback and saloon bodywork and touting five engines ranging from a 130bhp diesel to a petrol-powered 260bhp twin-turbo, all-wheel-drive V6. These will be joined in the new year by an estate body, and two more engines — one a mid-spec 180bhp petrol, and the other a twin-turbo 190bhp diesel.

While it was fun roaring around the Austrian Alps in the enjoyable, high-powered petrol variants — the 2 litre, 220bhp turbo version with optional four-wheel drive is particularly satisfying — it is the humble, basic diesel that will sell in the greatest quantities.

And this is where the Insignia has a problem. In any range of cars there will always be an optimal model which, if its maker has done its sums right, will be the one destined to sell in the largest numbers. The Insignia’s greatest rival is the 2 litre diesel Ford Mondeo, which, of all the models in a very wide range, is the most rounded and satisfying. The same cannot be said of the 2 litre diesel Insignia, however.

The engine is disappointingly noisy and provides only average performance. High gearing means it’s quiet enough at a motorway cruise, but it offers nothing in any other area of endeavour to distinguish it from the merely mediocre. Perhaps that’s why it has been priced some £1,610 below the more powerful and quicker Mondeo equivalent.

The shame is that Vauxhall has done good work in many other areas. The ride quality is sportingly firm but never harsh, the chassis offers exceptional composure on even very difficult mountain passes, the brakes are tireless and reassuring and the whole driving environment seems a world apart from that of the old Vectra. Indeed, in this respect, it sets the standard for the class.

While the interior succeeds in looking great, closer scrutiny reveals concerning imperfections. True, the cars I drove were early models, but not the sometimes shabby pre-production prototypes often foisted on journalists long before a car’s official on-sale date. Yet there was a preponderance of cheap, hard plastic on view, the handbrake of the diesel felt loose and flimsy, and when a colleague tried to use the electric controls to adjust the exterior mirrors, the whole assembly disappeared into the door.

Frustratingly, there is a very good car trying to get out of this Insignia. Its design is first class, and possibly the best in its category, but it is let down by execution. It’s too heavy, too expensive to run, and to the enthusiast driver, offers nothing beyond mere competency. With the Mondeo already established as the leading choice, both for drivers and owners, I fear a smart face and an attractive cabin will prove inadequate for combating a long-established class leader. Its single greatest strength at the moment appears to be keen pricing.

For now, though, the impression it left me with was not of how good it is (it only scrapes three stars), but rather, how much better it should have been.

Vauxhall Insignia Exclusiv 2.0 CDTi

ENGINE 1956cc, four cylinders

POWER 130bhp @ 4000rpm

TORQUE 221lb ft @ 1750rpm

TRANSMISSION Six-speed manual

FUEL/CO2 ACCELERATION 0-62mph: 10.4sec

TOP SPEED 127mph PRICE £16,935

TAX BAND D (£145 for a year)

VERDICT A step up, but misses target

RELEASE DATE December 2008