Mini’s new third-generation Convertible is bigger than before – but is it better? Or has removing the roof detracted from the fun driving experience of the already introduced three and five-door hatchbacks and six-door Clubman?

These are significant questions; it’s cabrio lore that only very clever engineering can ensure a platform rigid enough to withstand the structural pressures caused by removing the roof, yet avoid the traditional weight penalties that can transform a svelte hatchback into a lumpen, shimmying drop-top.

Mini prides itself on such skills, and exhibits them in this newcomer which, despite its larger body and additional chassis strengthening and stiffness over its Convertible predecessor, weighs in at a mere 25kg more. It’s that sort of clever thinking that netted the brand a record 338,466 sales in 2015 alone.

We drove the Cooper S ahead of its April showroom launch. It’s the headline 189bhp 2.0-litre model from a trio of more efficient, better-performing petrols and diesels, with more engine options to follow.

The new Mini’s styling has a more mature feel than previously, with an imposing grille, distinctive oval headlamps and larger tail-lights. Climbing aboard, what’s immediately obvious is the additional cabin room and versatility.

Minis have often been criticised for their passenger space, particularly in the rear, but those boosted body measurements result in noticeably more comfortable seating positions all round. It’s complemented by enhanced equipment levels over the second-generation car’s.

Meanwhile, the boot capacity – never a Mini strong point – has been boosted by 35 litres to 215 litres roof-up and 160 with the top stowed. This can be boosted by folding the standard-fit split seatbacks, while a wider external opening adds to the versatility.

Talking of the all-important hood, the entire set-up has been redeveloped. The fully electric, multi-layer cloth roof can be lowered to either a semi-erect position or dropped completely, whereupon it sits jauntily on the deck but rather unfortunately obscures the rear vision somewhat. The entire lowering process takes 18 seconds at up to 19mph.

Concessions to soft-top safety include a reinforced screen frame, automatically extending rear rollover bars, plus hidden bodywork strengthening incorporating beefed-up suspension-tower strut bracing and sill stiffing.

So far, so good – but what we want to know is what this Mini is like on the road. Well, we’re pleased to report that it’s highly engaging. The new 2.0-litre four-cylinder turbo’s 9bhp/20Nm boost really makes itself felt on the move, giving extra refinement and tractability over the previous 1.6-litre turbo. Teamed with a standard-fit six-speed manual transmission – a six-ratio auto with steering-wheel paddles is optional – electronic diff lock, Dynamic Stability Control and traction control, it delivers smoother, enhanced performance and response. Both low-down urgency and mid-range flexibility are better, too, resulting in a 7.2-second 0-62mph dash.

All-important handling and ride prowess is the main test of the Convertible’s abilities, and the good news is that dynamically the Cooper S is very well sorted. Unique tuning with individual spring and damper settings mark out the chassis, while our test car also sported optional driving modes in Sport, Mid and Green configurations.

The car is nippy and manoeuvrable on city streets, and exhibits great balance and grip on fast, out-of-town B-roads. Its steering is nicely weighted and direct-feeling, while any body roll is well controlled. The occasionally harsh ride can be tempered nicely in Comfort mode, and makes for a more relaxing drive than before over long distances. All that chassis stiffening has done the job, too, resulting in a more taut, well braced experience, with rarely any flex or scuttle shake transmitting through to the driver.

Just as you’d wish when spending a £3590 premium over the hatchback equivalent’s, this is a fast and engaging machine. Its smoother performance, enhanced refinement and zest on fast, twisting roads makes it a real joy to hustle along, and negates all those convertible clichés of old. For charisma and involvement the cabrio is a more rounded and desirable car than ever – and not only for those looking for a lifestyle machine. Mini has done itself proud.

Mini Cooper S Convertible Sport Automatic

On sale: March 2016

Price: £25,485

Engine: 4cyl, 1998cc, turbocharged, petrol

Power: 189bhp at 5000-6000rpm

Torque: 207lb ft at 1250-4600rpm

Gearbox: 6spd auto

Kerbweight: 1295kg

0-62mph: 7.1sec

Top speed: 142mph

Economy: 50.4mpg (combined)

CO2/tax band: 131g/km, 21%

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