BMW M6

Would suit: Alan Sugar
Price: £80,755
Maximum speed: 155mph, 0-60mph in 4.7 seconds
Combined fuel economy: 19mpg
Further information: 01344 426 565

I've not always been very kind about BMW owners. While their cars are usually hard to fault - apart from the 1-Series, of course - they seem to be driven by angry businessmen and skinny women (role models: Alan Sugar and Teri Hatcher). In a rash moment in one piece, I may actually have branded all BMV drivers as "bad people". This was a stupid thing to say, for all sorts of reasons, not least because I used to own a BMW.

My model had little in common with the new BMW M6 I tried this week, however. It was an old crock that had escaped from a scrapyard under cover of darkness and spent some time foraging in the woods before being trapped by the second-hand car dealer who sold it to me. It went very, very slowly. Because it had an iffy carburettor and dodgy brakes, it did this even when I would have preferred it to have stopped, so I often had to plan ahead to ensure there would be a bollard or wall to bring me to a halt, at which point I would jump out, lift the bonnet and fiddle with the carburettor until the engine died. Visits to marinas were a no-no.

If the throttle were to stick open on an M6 - assuming it had something as rudimentary as a throttle - it would probably keep going until the petrol ran out. This is a mighty thunder-hammer of a car, not only unimaginably fast but very big and heavy as well. There would be M6-shaped holes in buildings and walls in a straight line from here to, well, not very far actually. On several occasions, the dashboard told me I was burning petroleum at a rate of 7mpg, which made even me feel a little guilty. But, I mused, as I pumped my family's weekly food budget into the tank, perhaps its horrendous thirst and piddling 70-litre tank are some kind of safety feature: in the event of the driver falling asleep with the cruise control on, the damage will be minimised.

Actually, heart failure would be a more likely scenario involving a runaway M6. The technological trickle-down from Formula 1 to road cars is usually overstated - mostly by advertising copywriters - but the 5-litre V10 engine that powers the M6 owes more than usual to BMW's synergy (as they most likely call it) with Williams, not least its electrifying shriek and super-quick, seven-speed paddle-shift gearshift. Press the magic "M" button and those shift times are tightened even further, the throttle response is quicker, the dampers become firmer and the traction control lets you scare yourself a little more than is strictly necessary. The M6 is Ferrari-quick in a straight line. Despite its considerable bulk, and thanks, in part, to those steamroller rear tyres, it corners almost as quickly too - faster certainly than an M5, which carries an extra two doors and is 50kg heavier than its rakish two-door sibling.

But is the M6 worth £18,000 more than the M5, bearing in mind it is less practical and will probably depreciate more? I suspect only a small minority of bad-tempered, chippy millionaires will be inclined to think so (although, compared to the Bentley Continental GT, it's a bargain), but nevertheless I found it intoxicating. "You're fired!" I hollered at my two-year-old as he spilt Ribena on the carpet, a day after the M6 arrived. Then I commanded my wife to "pull her finger out" when unpacking the dishwasher. Funny how you bruise so much more easily as you get older...

It's a classic: BMW Z1

For all its macho posturing, I have a sneaking affection for the M6, but the BMW I yearn for more than any other has to be the Z1. This pert little two-seater roadster was never meant to be a production car and, in fact, grew out of a test bed for a new suspension system for the 3-Series.

Its impromptu origins allowed the BMW design team an unusual degree of latitude when it came to the Z1's looks - at that time, the company was known for its sober saloons - and so they gave it a radical wedge-shaped profile and clever glass-fibre doors which, instead of hinging outwards, dropped down into the sills. Public demand ensured the car went into production, with a 2.5-litre straight six.

Despite its light weight, the Z1 managed just 140mph top speed and 0-60 in 7.9 seconds, but it reportedly handled with typical BMW finesse and built a loyal following. Over 8,000 were sold and their second-hand values have held solid ever since.