WHEN it comes to high performance convertibles they don't come more loaded than the BMW M4 - the drop top version of the mighty M3.

For a shade under £65,000 this is open air motoring of the highest order in a car with a race track pedigree.

In the current BMW stable the M4 picks up where the previous generation M3 coupe and convertible left off in line with the company's latest model structure of giving saloons and estates odd numbers with even ones reserved for the more exotic shapes.

Nevertheless the M4 shares much with the new M3 saloon but both the coupe and the convertible cost more - some £5,000 in the case of the convertible.

With its retractable hard top the M4 convertible weighs in at 1,825 kilos making it 230 kilos heavier than the saloon.

That's reflected in a slight drop in performance - although you will hardly notice that it takes 4.4 seconds to go from nought to 60mph compared to 4.1 seconds in the saloon.

Those figures are for the models fitted with a seven-speed DCT gearbox - a £2,645 extra over the standard six-speed manual taking the price to £63,795 - and in this set up the M models are at their finest.

You can hear the semi-automatic box coming to life when moving off but once under way it is smooth and seamless, even when used manually via the paddle shifters or from a flick of the gear lever itself.

Multi-mode drive configurations allow the car to be switched from eco to a choice of two sport modes and the gear intervals can also be altered as required such is the flexibility of the driver-oriented software.

Preferred settings can saved behind one of two M mode buttons on the steering wheel to engage in an instant, unleashing what the M4 is all about.

The sound from the four exhausts is enhanced to create a purposeful roar under acceleration and roof down it's an experience to savour - it's not that bad with the roof up either.

Roof retraction takes just over 10 seconds and is done at the push of a button aft of the i-Drive control pack which governs the onboard communications, entertainment and navigation equipment.

For convenience, the roof controls can be concealed beneath a sliding centre console lid if desired.

With the roof down boot space is restricted to a couple of overnight bags and even when up luggage capacity is only 220 litres and that's half of what the M3 can carry - although both are fitted with a ski-hatch.

The convertible is a four-seater with a modicum of rear leg room and despite the seat backs being quite upright, it will seat four adults without any compromise.

Wind noise and bluster is well subdued and there are air blowers in the front head restraints if conditions are on the chilly side.

Roof up or down the M4 looks the part with muscular lines defined by a power bulge on the bonnet - a characteristic of BMW's M models.

Inside, it is plush and sophisticated with leather trim, carbon fiver inserts and a full suite of technological systems available via a 10.8-inch touchscreen.

This particular car was fitted with an optional head up display - an invaluable feature on a performance car presenting the vehicle's speed and sat nav information in the driver's line of sight - and it gets more interesting with the M buttons engaged as it shows the rapidly changing sporting prowess of this thoroughbred.

Like the M3 it is fitted with a 3.0-litre six cylinder turbo engine boosted to pump out 431bhp and the power is plentiful whatever the speed.

Fuel economy is rated at 32.5mpg which is some five per cent off what you can expect in the saloon and in the real world it returned close to 28mpg.

Emissions for the DCT version are rated at 203g/km giving it a tax banding of 35 per cent for business users, two per cent below the manual M4 convertible which comes in at 213g/km.

That level of fuel efficiency is more than acceptable for a car with such venom and with top notch handling the M4 delivers on all fronts, transforming in seconds to satisfy any whim.

This is a car with rear-wheel-drive purity enhanced by sophisticated electronic traction systems designed to deliver the best - and it will whatever the season.