The range has a slightly larger choice of petrol engines. The 118i and 120i both have 2.0-litre units, but they are relatively sluggish. The other models have 3.0-litre six-cylinder engines – with 215bhp in the 125i, and 302bhp in the twin-turbocharged 135i – and pull strongly. There are also three diesel engines, with the mid-range 174bhp 120d our favourite.

In the conversion from coupe to convertible the 1 Series has lost a little sharpness, but few drop-tops at this price are as much fun to drive. Crucially, the body is stiff, so the steering remains precise and informative and the handling is grippy and well balanced. The ride is well controlled and generally comfortable, but the run-flat tyres thump over sharp bumps.

The 1 Series has a folding fabric roof, whereas many of its rivals have a metal one. It’s impressively refined nonetheless. There’s some wind noise at speed, but road- and suspension noise are subdued and the engines are particularly smooth and quiet. The major controls work with well oiled precision and the Auto Start-Stop system on four-cylinder models is seamless.

Prices are high for such a compact car, but BMW convertibles hold their value well. Fuel economy and CO2 emissions are competitive across the range, but six-cylinder models won’t be cheap to run. The 120d, on the other hand, makes lots of financial sense, with average fuel economy of 55.4mpg and CO2 emissions of just 134g km.

Inside, familiar BMW architecture confronts the driver. The clearly marked instruments and tactile buttons, stalks and switches all have the same quality feel of more expensive models from BMW's portfolio. Some of the plastics aren’t as appealing as its pricier models, but the overall ambience is classy and BMW’s recent reliability record is good.

Like every BMW, the 1 Series has stability control and the latest electronic braking aids as standard. The Convertible has front airbags and side airbags that cover the body and heads of those inside. Metal bars pop up from behind the back seats to give protection if the car starts to roll. Deadlocks help to deter thieves, but the fabric roof is more vulnerable than a metal one.

The 1 Series’ driver’s seat is a good place to be, with a simple dash and an excellent driving position. Even the lankiest driver will be able to get comfy, thanks to a wide range of steering wheel and seating adjustment. If you don't specify electrically adjustable seats, however, you'll need to pull on levers and shift your weight to adjust their height and angle.

There’s plenty of space up front, but BMW’s claim that the 1 Series Convertible is a genuine four-seater is optimistic; rear legroom is tight and the steep backrest angle makes even short journeys uncomfortable. The roof folds down electrically in 22 seconds and, with it stowed, the 260-litre boot is big enough to hold your luggage for a weekend away. When it’s up, you can push the container that holds it out of the way to gain an extra 45 litres of space.

Entry-level ES versions have four electric windows, air-conditioning, alloy wheels, an MP3 input socket and automatic headlights and wipers; Sport versions add 17-inch alloys, sports seats and front foglamps. SE trim brings extras such as front foglights, climate control, rear parking sensors and a multifunction steering wheel, while M Sport gives a bodykit, larger alloys and lowered suspension.