In theory it's easy to dislike big convertibles. They're brash, showy, fuel guzzling tributes to propping up an overinflated ego, yet at the same time it's impossible not to warm to their sheer brass neck. The BMW 6 Series Convertible is a case in point. You'll need to be very comfortable with the notion of being stared at and although you may well achieve this end a good deal more cheaply by leaving home in the morning bereft of clothes, you wouldn't relish the prospect of 155mph with your bits blowing in the breeze. The 6 Series Convertible makes exhibitionism seem wholly acceptable.

The hood mechanism isn't of the currently fashionable folding hard top variety, instead being a more conventional fabric affair capable of disappearing from view in less than 20 seconds. The best part about the hood is that it's operable with the car moving at speeds of up to 20mph. Much quicker than that and aerodynamics would plant your hood onto the windscreen of the car behind but it's nevertheless very impressive to be able to drop the hood while on the move. Six hydraulic cylinders guide the ragtop into place without significantly compromising luggage space - a major issue with folding hard topped cars.

This is the facelifted 6-Series but you'd really have to eyeball one parked alongside the original car to pinpoint the changes. For the record, the headlamps have the LED technology that is so popular amongst the premium marques at the moment. It takes the form of a thin row of lights above the main projectors. More obvious is the redesigned front valance that accommodates differently shaped air intakes and at the back the bumper has been tweaked it increase the impression of width. Other than that, the grille is fractionally larger and the rear light clusters have been tweaked.

"It's a car that will brighten even the greyest of days.."

The Convertible retains the coupe model's near 50:50 weight distribution and the car's contours are preserved with C-pillar style fins. Many soft-top cars look a million dollars with the roof down but around a hundred with the soft top in place. The 6 Series also features a retractable glass windows and noise insulating polyurethane foam sandwiched between the rubberised outer membrane and the inner hood fabric.

The designers have done their best to minimise wind noise and a quick trip through a car wash will show that water ingress just isn't worth worrying about. The shape of the car directs airflow away from the passenger compartment and at speeds of over 100mph, front passengers will encounter very little in the way of turbulence. With the roof in place, the boot offers a generous 350 litres of space and 300 when it's folded. Manufacturers love to measure capacity in terms of golf bags (target market) and this boot is capable of carrying two.

Priced from £54,945, the 6 Series Convertible is currently available with two mainstream petrol engines and both are mighty pieces of work, now made more powerful yet more efficient through BMW's clever EfficientDynamics technology. The 630i now packs a 272bhp six-cylinder unit capable of 0-60mph in around six seconds and yet this is the affordable face of 6-Series convertible ownership with a very reasonable combined fuel consumption figure of 34.0mpg. Even the 4.8-litre V8 650i Convertible manages 22.4mpg, up 7% on the previous version. Yet it wafts to sixty in 5.5s.

Arguably the 6 Series Convertible to have however, is the 635d diesel version. Yes, you read that right. Diesel engines don't traditionally sit well in luxury convertibles but this 3.0-litre twin-turbo isn't a traditional diesel. It's slightly slower on the 0-60mph measure than the 630i but the engine's crushing peak torque of 580Nm is served up from just 1,750rpm, making it devastatingly fast in real world conditions. The 635d's surging acceleration has more in common with that of the range-topping 650i. Ring its neck and a supercar-esque 6.6-second 0-60mph sprint can be extracted. It would bludgeon through the 155mph barrier too, if the artificial limiter were not on guard. Yet it will record 39.2mpg on the combined cycle.

The 630i and 650i comes as standard with a six-speed manual gearbox, while the 635d is offered with a desirable six-speed sports automatic transmission. This gearbox features a clever torque converter with enhanced software and a two-stage damper to reduce vibrations. The improved transmission specification means power-wasting slip in the converter is largely eliminated and the slicker software results in gearshift times that are smoother and 50 per cent quicker.

Although the 6-Series Convertible can lift its skirt and hustle when needs be, it's by no means an out and out sports car. The ride is firmer than you may expect, the big tyres occasionally crashing through potholes. Dynamic Driving Control is a function very similar to the 'Sport' mode on the M5 and M6 models. Press a button on the centre console and this sharpens up throttle reaction as well as generating a little more feel from the steering system. When allied to the SMG or Steptronic gearboxes, DDC also shifts gears at higher revs, switching ratios in just 150 milliseconds. Whichever system you choose, you'll be amazed at the sheer grip generated by the roadroller Bridgestone Potenza tyres.

An option many customers will choose is BMW's Dynamic Drive. This automatically builds up counter forces on the car's anti-roll bars and as such, virtually eliminates any body roll when cornering. Even without options of this kind selected, the 6 Series is still a very nice place to do business. Core driving functions are located in or around the steering wheel and a simplified version of the iDrive system offers a still enormous amount of driver control with just a few nudges, taps and twists of the serrated metal mouse.

The dashboard design is otherwise rather low key, the analogue dials being rather disappointingly small. If the exterior is jam-packed with design details clamouring to catch your eye, the opposite is true of the cabin layout. Yes, it all hangs together very well and seems well built but nowhere does your eye alight approvingly on a signature feature. Automatic air conditioning and a very respectable stereo are fitted but some small omissions grate. Fold the front seat forward to climb into the rear and despite there being electric movement for the seat, it stubbornly stays in place.

BMW plan to import just 1,000 Convertibles a year, so unless you live in Alderley Edge or Guildford, it's unlikely they'll become common currency. For those of us unable to stretch to one, that is a shame. It's a car that will brighten even the greyest of days.

TOP 4 6 SERIES DEALS

The results below show the top 6 SERIES deals on buyacar

	BMW 6 Series 650i Sport 2dr Auto Convertible
	ETR	Mthly	Saving £3,698	Price £61,787
	BMW 6 Series 650i 2dr Convertible
	ETR	Mthly	Saving £3,456	Price £58,609
	BMW 6 Series 650i 2dr Auto Convertible
	ETR	Mthly	Saving £3,567	Price £60,068
	BMW 6 Series 650i Sport 2dr Convertible
	ETR	Mthly	Saving £3,587	Price £60,328