This is Audi’s plush, range-topping, four-seat open-top GT. At £47,035 the ‘basic’ S5 cabriolet comes with a 328bhp supercharged V6 engine, four-wheel drive, subtly expensive styling inside and out, beautiful sports seats and an impressively well-sealed fabric roof.

In its standard guise, it is very rapid and secure and handsomely stiff. It certainly delivers a satisfyingly premium experience, from the LED downlighting in the footwells to the creamy power delivery.

However, I can’t deliver the definitive verdict on the typical S5 because the car tested here was fitted with some very trick, optional electronic chassis aids, which really transformed the car’s character.

The ‘Technology’ and ‘Drive Select’ packages (which cost £1750 and £1290 respectively) offer the driver switchable changes to the responses of the steering, dampers and engine.

This car was also fitted with Audi’s torque-vectoring Quattro sports differential (£460), which can apportion the twist action in differing amounts between the rear wheels.

In Comfort mode the S5 saunters lazily. The steering is vague and the ride loose-limbed. In Auto mode, though, the car pulls together, working as a more of whole. I did, though, find it a touch remote and artificial and sometimes hard to place on narrow roads.

On a fast Sussex B-road it also needed use of the paddle shifters to extract the best from the engine in Auto mode. (You should also specify the automatic high-beam headlights for these conditions, as it’s impossible to paddle shift and beam switch at the same time.)

In Dynamic mode, however, the S5 went through a complete character change. The steering responses are much sharper, as is the engine’s pick-up. Stiffer damping seems to help the ride.

Driven hard into bends, this S5 had supernatural levels of lateral grip, fabulous stability and virtually no roll. The chassis simply tears at the tyres’ grip during hard driving.

It steered surprisingly well, relished being pushed hard and could be placed with laser precision. The shorter V6 engine (the S5 coupe still has the V8) must help to reduce nose-heaviness.

But fitted with the various elements of Audi’s dynamic chassis technology it lunges remarkably close to being a serious driver’s car, despite the reduced body stiffness inevitable in a cabrio.

A car like this goes beyond rational calculations. If you can afford it, you’ll love it. A similarly specified S5 coupe - powered by the V6 engine - might well be one of the best driver’s cars ever to wear the four rings. If only Audi would build it.

Audi S5 Cabriolet

Price £47,035 Engine V6, 2995cc, supercharged,  petrol; Power 328bhp at 5500-6500rpm; Torque 327lb ft at 2900-5300rpm; 0-62mph 5.4sec; Top speed 155mph; Gearbox 7-spd dual-clutch automatic; Kerb weight 1880kg; Economy 34.9mpg; CO2 189g/km

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