Features

18:30 The problem with this drop-top is that you lose 140 litres of boot space when the roof's in it, so don't expect to get your golf clubs in here. Or even a large suitcase. This is easily overcome by not having any friends, which allows me to use the fold-flat rear seats to carry my luggage.

These are a handy feature and should appear by law in every cabrio made. This M3 is definitely more conspicuous than the last cabrio, and has become gauntlet-like to macho types who Will. Not. Be. Beaten. Especially not by a tattooed guy in a silly hat and sunglasses. Every Porsche driver is determined to get past. I 'let' most of them go. I said, 'let'.

19:30 TUNNEL! Finally! I thought I'd never find one. There's nothing quite so smile-inducing as the sound of a high- revving V8 bouncing off the walls of an enclosed space. Grins per gearchange are redlining. An appreciative truck driver waves encouragement. I don't need any.

The sun's setting. It's interesting how much more sky you can see without a roof. The sky looks big, and the clouds are making crazy patterns.

20:30 A crisis of confidence has kicked in, and I don't think I'm going to make it all the way back to London in one go. It's raining again and, with the roof up and the heating on, I begin to find I'm getting too comfortable, too cosy, sleepy.

20:45 It's getting silly now. All I can think of is a nice hotel bed. Shall I bail on my boy mission and just stop? I ask the lady-voiced satnav. She tells me to carry on this road for another 90km. Is that advice or a challenge?

20:50 AC/DC: 'We rock at dawn on the front line/Like a bolt right out of the blue/The sky's alight with the guitar bite/Heads will roll and rock tonight.'

21:00 I'm pulling over. Comfy seat. Heavy eyelids. Sleep.

21:20 That's better. Power naps should never be dismissed. I pop into the garage for a can of Red Bull and a man-sized pack of pretzels. Roof and adrenaline up, I'm back on the road.

21:30 I'll give it another hour or so and see how I feel. It's not that far to go now. Not really. Maybe I can do this? Come on!

22:00 Night-time open-air driving is another thing entirely. It's not what you'd expect. The cliche for roofless driving is top-down in sunshine. But night-time is just as good. Fast lights, moon, stars - it's all part of the M3 cabriolet's repertoire.

23:30 Conclusion after so many hours is that this M3 cab is a tremendous car - heavier than the coupe, but still a proper work of automotive art. The roof-down advantage should not be dismissed, and for most fast driving, you won't feel the extra weight either. Maybe this M3, with this gearbox, is the M3 of choice?