Vauxhall performed a neat marketing trick a couple of years ago when it announced that it had replaced the Insignia VXR with a new model called the SuperSport.They key claim about this car was that in saloon form with manual transmission it was the only car on sale in the UK for under £30,000 with a top speed as high as 170mph. This is still true, and it's an impressive thing for both the company and its customers to be able to say.It was achieved easily enough. All Vauxhall did was knock several thousand pounds off the list price (which suggested that the previous VXR had not been at all popular) and revised the electronic speed limiter so that it cut in 15mph higher than the previous 155mph. The car wasn't actually quicker in any important sense - it was simply allowed to continue accelerating for longer than before.Further changes were made last year. Most of them related to the interior and exterior styling and were shared across the whole Insignia range, but the SuperSport also had its rear suspension revised to improve the handling.That brings us to the present day. The manual saloon can still be yours for a shade under thirty grand - or, to state the case more precisely, £29,824 - but what we're talking about here is the obviously more practical Sports Tourer estate, which costs £31,124. (Automatic transmission, with the usual pluses and minuses, is available in each case.)In most driving situations, it's a very appealing car. The turbocharged 2.8-litre six-cylinder petrol engine sounds great because the exhaust system has been designed to make sure it does, and with up to 321bhp available it gives the SuperSport sturdy acceleration which will prove useful if an overtaking opportunity suddenly arises, or if you're crying, "Stop, thief!" while chasing after a bank robber with a grateful gendarme in the passenger seat.More realistically, the SuperSport is a very capable high-speed cruiser, and if the road you're on happens to permit relaxed but purposeful wafting, then wafting of that precise nature is what is going to happen. It's almost as if the "sport" part of its name actually describes what the car does.But in fact this is not the case, as you'll discover if you find yourself on a more challenging road. It will soon become apparent that either you have to accept you're not going to be able to maintain the sort of average speed you might have wanted to or you should have bought something else instead, because this Insignia will allow itself to be hustled only up to a certain point.If you attempt to go beyond that point, a curious diagonal pitching motion takes over. The car no longer wants to play, and your stomach doesn't want it to try. You could go quicker if you wanted to, because you're not yet in danger of being catapulted into the scenery, but it's not going to be any fun and you might as well not bother.So you wait until you reach a less stressful piece of road, and the Insignia once more becomes the quick and comfortable mile-eater it really wants to be. And if that's what you want, you made a good choice when you bought the car.To the extent that spirited driving is possible, the SuperSport feels very secure during it. The standard four-wheel drive is a big help here, of course, but so is the clever HiPerStrut front suspension, which works well on every Vauxhall I've driven that was fitted with it, and the Flexride adaptive damping. Brembo brakes also inspire a feeling of cautious confidence.As with all Insignias, the interior of this one is attractively designed, and while the level of equipment falls a little short of lavishness (the air-conditioning is only single-zone, for example), you do get Vauxhall's IntelliLink system, nicely supportive Recaro seats, automatic headlights and wipers, cruise control, hill start assist and a USB connection, which is okay for a large and powerful car priced similarly to a top-spec hot hatch. Engine 2792cc, 6 cylinders Power 321bhp Transmission 6-speed manual Fuel/CO2 25.9mpg / 255km Acceleration 0-60mph: 5.9 seconds Top speed 170mph Price £31,124 Details correct at publication date