BMW Z4

It's been in the 630i and 530i for a while now, but the new magnesium-blocked three-litre six finally makes it into the Z4 in this, the 3.0 Si. The basic differences are that there's a decent weight-saving from the use of slightly exotic metals and power is up to a healthy 265bhp.

Getting hold of the grunt isn't a problem. Double Vanos valve timing and electronic manifold-fettling help to keep the power delivery flatline linear, there's a bassy exhaust note that's not intrusive at speed and stomping through the notchy-but-accurate gearshift is no hardship at all - apart from the fact that the gearknob came off in our test car.

Truth is, this is a genuinely fast roadster that manages to mask its quite thorough annihilation of the benchmarks with a thick veneer of civility and day-to-dayness. Imagine describing 5.7 to 62mph and 155mph as merely 'quick' a few years ago - you'd have Lamborghini in tears.

In fact, the Z4 manages a neat trick of egging you on come playtime, but still holds things together perfectly well if you're trying to act like a grown-up. You can pull away from 20mph in sixth gear without a grumble - now that's tractable.

This SE version gets a long list of toys and electronics, as well as 17in wheels on Bridgestone Potenzas. It doesn't look under-wheeled and the smaller diameter, along with the lighter engine, helps to iron out the Z4's notoriously firm ride by having that extra rubber in the sidewall.

It's still a hard-riding car - there's a fair amount of jiggle if the road surface is bad - but still far better than the 'Sport' versions with 18in rims and stiffer suspension. Something to remember if you're going to use this car everyday - fashionable hoops can irritate your 3rd and 4th vertebrae.

The most convincing argument is a pretty simple one. Personally, I've always quite liked the 2.5-litre Z4 for a combination of handling and power balance, but the 3.0 Si very neatly shades it. Roughly £4k brings you the 3.0Si SE instead of the 2.5Si SE, but even at that price, it still knocks off a whopping £10k from Z4M list (£42,795).

Yes, the M car might look two or three biceps more committed, but the Z4 is a pretty shape without all the slap-happy spoilers, and the 3.0 Si makes a rather overwhelming case for the fact that 265bhp is pretty much on the button for the Z4's suspension and chassis set-up. We like.

Tom Ford