You’re looking at Vauxhall's new big-saloon flagship. The perceived decline in demand for large cars over the past decade hasn’t done much to harm the UK success of the Vauxhall Insignia.

Luton counts the 4.9-metre-long exec as one of its successes — one good reason why it has unveiled this new version, now called the Insignia Grand Sport. First deliveries are planned for late in June, with a revised Sports Tourer due later in the year.

Prices, some revised downwards by as much as £1500 to fit new benefit-in-kind (BIK) tax categories, start at £17,115 for the entry-level Design model powered by a new 1.5-litre, 138bhp engine, and peak at £27,710 for the 2.0-litre, 256bhp Elite Nav 4x4, which comes complete with an eight-speed automatic gearbox, an exceptionally deep specification and full-time four-wheel-drive.

There are three petrol and three diesel engines on offer, starting with the 108bhp 1.6 diesel, which delivers the range’s headline CO2 figure of 105g/km. It is followed by a 134bhp version of the same engine, and a 168bhp 2.0-litre diesel, while the petrol range is made of two variants of Vauxhall’s new 1.5-litre petrol in 138bhp and 163bhp forms, while topping the range is a 256bhp 2.0-litre unit. These engines are shared across the Grand Sport and Sports Tourer.

Since the launch of the original model in 2008, the Insignia has consistently delivered a bloody nose to two tough Volkswagen Group competitors, the Volkswagen Passat and Skoda Superb, and has also matched blows with premium saloons from Mercedes-BenzAudi and BMW that have lately dropped into its upper price echelons.

However, with this new 2017 Insignia Grand Sport, Vauxhall says it’s getting serious. The Insignia now has all-new coupé-like styling reminiscent of the company’s 2013 Monza concept, a 92mm-longer wheelbase and a 55mm-longer body (now 4897mm overall) which allows for more leg, head, shoulder and hip room in the rear — previous points of criticism — and luggage space practically as big as the old models’ vast enclosures.

The more graceful shape results from a lower scuttle, a longer bonnet (which is now aluminium), a prouder, more vertical front grille, narrower headlights (including new LED, 32-element IntelliLux units, a £1010 option), a longer wheelbase and sculpted body sides that present Vauxhall’s familiar blade-like styling element in a new way.

The Insignia Grand Sport comes with wheels varying in diameter from 17in to 20in depending on specification, but all models have the same spring and damper rates for their all-independent suspension. A Tourer (estate) version carrying a £1500 premium is due soon after the saloon and a higher-riding Country Tourer model is due at the year-end.

As for trims, there are seven trims to choose from, with entry-level Design models coming with automatic lights, electric windows, air conditioning, cruise control, keyless entry and start and Vauxhall’s 7.0in IntelliLink infotainment system complete with DAB radio, Bluetooth, smartphone integration, USB connectivity and OnStar assistance package.

Upgrade to SRi adds 17in alloy wheels, front fog lights, auto wipers, climate control, rear USB sockets and sports seats, while opting for Design Nav or SRi Nav equips your Insignia Grand Sport with sat nav and an 8.0in infotainment screen.

SRi VX-Line Nav models get a VXR bodykit, heated steering wheel and a 4.2in colour information display as standard, while opting for Tech Line Nav includes parking sensors, lumbar adjustment and touches of chrome.

Topping the range is the Elite Nav trim which adds leather upholstery, heated seats, IntelliLux LED headlights and a Bose sound system.

Like the current Astrathe Insignia delivers a startling weight saving right across the range: up to 175kg, model-for-model, of which 60kg comes from the body alone. The car is also impressively aerodynamic. Design chief Mark Adams cites the simplicity of the sleek lines as one reason for an impressively low drag factor of 0.26. The interior is similarly impressive: it is simple, drawing inspiration from the clean surfaces of the exterior, and from Adams’ preoccupation with simple logic for switch design and layout. Best of all is an enhanced aura of quality, inside and out.

Getting to grips with the Insignia Grand Sport

On the road, the new Grand Sport has the same relaxed, easy-cruising feel as its predecessor, but improved. Its slight increases in length and width aren’t detectable from the driving seat, though when you set it up for a six-footer, there’s still decent generous room for same in the rear. Our test car, a mid-spec Insignia Grand Sport Tech Line manual retailing at £23,910 (with £3900 worth of accessories that included the IntelliLux headlights, a newly-offered £705 glass sunroof and £555 worth of two-coat metallic paint) had the more powerful of two 1.5-litre petrol versions, packing 163bhp claimed to give it an 8.4sec 0-60mph time and a 138mph top speed.

The peak torque of 184lb ft, developed between 2000 and 4500rpm, felt even more relevant to the car’s performance, however, because one feature especially relevant to UK motorways was the car’s relaxed gearing (2500rpm at 70mph) and another was its surprisingly strong top-gear acceleration around that speed. The six-speed manual gearbox is sweet-shifting and its action matches the clutch perfectly, but once the engine is turning beyond 3000rpm, it gains speed in high gears without effort or noise.

This model/engine combination turns in combined fuel consumption of 47.1mpg, while emitting 136g/km of CO2, which promises day-to-day consumption in the late 30mpg bracket. With the 65-litre fuel tank, the car should have an easy cruising range of 460 miles-plus.

The Insignia Grand Sport’s long wheelbase and wide track make this a very stable car with excellent directional stability. The 17in wheels on the car we tried were very good at damping higher frequency surface disturbances, but we get the feeling that bigger wheels with classier rubber would have sharpened the steering, which is okay, but still fails to stand out. They might increase tyre noise, though, which is already no better than average in a class that contains some good performers.

Overall ride comfort is better than before, and just about ideal for a car like this: flat and notably quiet over bumps, with a decent level of damper control that promotes good grip and near-neutral handling in fast corners. Brakes are powerful and easy to modulate. Even so, the 'Sport' in this car’s title shouldn’t be taken literally. The Grand Sport’s engine is smooth and quiet, and its wind noise is commendably low.

Is the Insignia Grand Sport a worthy successor?

In the new Insignia Grand SportVauxhall has repaid its supporters’ eight years of solid support by digging deep to give this replacement a whole raft of worthwhile changes that improve the looks, the space, the handling, the economy and the comfort. And in strategic places, the prices are lower, too.

In short, Vauxhall’s biggest saloon looks a better proposition than ever.

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