"That's the 400bhp engine, is it?" It's not often that you get pleasantly accosted at traffic lights these days, but the bloke in a Mini next to me was obviously keen to determine all that power really was crammed into an RS4 Cabriolet (£59,625).

And he was right to be cynical, because when a car maker develops a cooking engine and drops it into a cabrio, the engineers often knock its power back a peg or two. Volvo's done it with the C70 D5 after all, and that's hardly a sports car.

But no, with the RS4 what you see is what you get. So that's 414bhp (Mini-man was out a fraction) and 317lb ft, both identical to the saloon's output. And we all know how quick that beast is.

So, although the cabrio weighs an extra 195kg, it can still sprint to 62mph in 4.9 secs. This is staggeringly quick, but it's the easy access to the power that makes it so addictive.

The RS4 pulls strongly from low revs and keeps on going 'til the high-for-a-V8 8,250rpm redline. So, you're as happy tooling around at low speeds as you are blatting down a B-road.

Plus, roof down, it sounds fantastic. And you can press the Sport button on the steering wheel for a few extra aural delights, as this opens a baffle in the exhaust to add some bite to the note, as well as sharpening the throttle response.

What you don't get in the Cabriolet are the winged seats that come in the saloon and pump themselves up when you hit the 'S' button, because they restrict access to the rear too much.

What's so impressive is that you can summon all this pace without feeling like the car's going to fire you off into the nearest hedge. Audi says the chassis is unaltered between cabrio and saloon, so you've still got four-wheel drive and sports suspension.

This gives you the same amount of confidence in the corners as you get in the saloon because everything feels so secure. Sadly, though, while the cabrio is good, you don't get quite as much feel through the chassis as you do with its roofed brother.

The scuttle shake doesn't help. It's not bad, but at higher speeds on rough roads with the roof down you can really feel it's there. Overall, though, this is minor because the RS4 copes admirably with all that power and far better than you'd expect - Mr Mini can rest easy.

Piers Ward

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