The M3 is powered by a 4.0-litre V8 that churns out 414bhp and 295lb ft of pull. It responds almost instantly in any gear from almost any speed, and sounds fantastic all the way to its 8400rpm redline. From a standstill, it will race to 62mph in just over five seconds, while the mid-range oomph is so strong there's no need to thrash the engine to travel quickly.
Like the Coupe and Saloon versions, the drop-top M3 has a beautifully balanced chassis that delivers agile handling and astonishing grip. The removal of a fixed roof has inevitably compromised rigidity, though, so poorly surfaced roads cause the body to shudder and send some kickback through the steering wheel.
The engine produces a deep resonance, but otherwise the M3 Convertible is pretty quiet with the roof up. Front-seat occupants don't suffer much buffeting from the wind when it's stowed, either. The optional M DCT dual-clutch gearbox shaves a couple of tenths off the 0-62mph sprint and lets you adjust the speed and ferocity of shifts, but it can be a bit clunky during low-speed manoeuvres.
Every M3 comes with engine stop-start technology to cut fuel consumption in traffic, but you’ll struggle to get anywhere near the official 22.2mpg average if you work the engine hard. Company car users will pay tax at the maximum 35% rate, while insurance premiums will be stiff. Thanks to a loyal following for the car, resale values are strong - even stronger than on the coupe version, in fact.
The M3 Convertible is expensive, but it has the quality to justify its pricetag. The look and feel of the interior fittings, and the way they're put together, is exemplary. BMW also has a reputation for mechanical solidity, and this model shouldn't do anything to damage it.
A coupe-cabriolet is always going to provide a sterner test for thieves than a soft-top - one of the reasons why they are now so popular. The long list of standard safety kit includes stability control, self-drying anti-lock brakes, two front airbags, body-and-head side airbags and automatically activated roll-over hoops.
The M3 Convertible's folding metal roof gives you a far better view of what's behind than a traditional fabric hood. The seats are supportive, there's a huge range of adjustment and the dash is similar to lesser 3 Series models, which means it's clear and logically laid out. However, many systems are operated through BMW's iDrive controller, which can seem complicated until you're used to it.
Space in the rear for tall adults is noticeably tighter in the back of the Convertible than in the M3 Coupe. Boot space is also limited, but the rear-seat backrest folds down to create a flat luggage platform and there's a hatch in the seat from the boot for skis and golf bags.
The M3 is no stripped-out race replica. Features such as automatic wipers and xenon headlights, part-leather sports seats, electric adjustment for the driver's seat and satellite-navigation supplement the basics of 18-inch alloy wheels, climate control and a CD player. You have to pay extra for full leather upholstery, larger alloys and Bluetooth connectivity, though.