Large cars from mainstream brands such as this new Insignia Grand Sport are perceived as something of a rarity these days. The market has shifted towards premium brands and SUVs, leaving models such as the big Vauxhall out in the cold. Try telling that to the British brand: sales of others may well have withered, but the Insignia remains strong.

The launch of this all-new Grand Sport version is thus a bit of a big deal. It’s on sale now with deliveries beginning in June – and we’re the first to drive it. Immediately, it’s clear Vauxhall is getting serious, with distinctive coupe-like styling that draws heavily from the Monza concept car that wowed the motor show crowds back in 2013.

Dimensionally, it’s bigger all round, with a 55mm longer body and 92mm longer wheelbase: at 4.9 metres long, Vauxhall hopes it’s cured the leg, head and shoulder room issues of the current Insignia. Yet this extra space doesn’t cost any extra. Indeed, priced have gone down, in some cases by as much as £1500.

They start from £17,115, which is more Astra-level than large family saloon money. Even the range-topping 256bhp 2.0-litre turbo Elite comes in at under £30,000. You can’t get much Audi A4 and BMW 3 Series for that, we can tell you. To the road, then, to find out if there’s a reason for this.

The spec sheet suggests things will bode well. The new Insignia Grand Sport is up to 175kg lighter than the old one, a whopping weight reduction. The sporty shape is slippery too, with a drag factor as low as 0.26. Importantly, it looks elegant, clean and simple, something that carries through inside as well. Again, a big improvement over today’s car.

It’s also easy-going to drive. It’s a car that doesn’t feel enormous, but does cruise smoothly and serenely, eating up the miles without fuss. This was all the more surprising given how our car had a smallish-sounding (but powerful) 1.5-litre turbo engine, producing 163bhp for an 8.4sec 0-62mph time. It had lots of pulling power, surprisingly strong motorway acceleration and an effortless, low-noise demeanour.

Motorway stability is excellent and most road surfaces are soaked up without fuss. Models with bigger wheels may spoil this a little, but they might also have sharper steering than our test car – one of the few criticisms was a slightly rubbery feel through the wheel. Otherwise handling was grippy, neutral and flat.

The new Insignia Grand Sport is a strong car indeed. Vauxhall has worked hard to improve it in pretty much every area, with significant gains in some. It looks great, has a nice interior, is a dream on the motorway and, most impressively of all, is cheaper than the old car. Who’s going to bet against Vauxhall continuing to defy convention with the new Insignia Grand Sport?

Vauxhall Insignia Grand Sport Tech Line 1.5 Nav

Price £23,910

Engine 4cyls, 1490cc, petrol

Power 163bhp at 5600rpm

Torque 184lb ft at 2000-4500pm

Gearbox Six-speed manual

Kerbweight 1500kg est

0-60mph 8.4sec

Top speed 138mph

Economy 47.1mpg combined

CO2/tax band 136g/km, 26%

Rivals VW Passat 1.4 TSI, Skoda Superb 1.4 TSI 150