The Prius is the world's best-selling hybrid petrol/electric car, the vehicle de choix of Hollywood stars. Its appeal in the US is largely environmental, for it has very low emissions. But here it is largely economic - it has extraordinary fuel economy; Toyota claims the best around town of any car on the British market. And all that for £17,500 to £20,000, depending on equipment.

So what do you get? Well, it is a biggish, nondescript looking, five-door hatchback. It has two engines, a 1.5-litre petrol one and the equivalent of a 1.2-litre electric one. Under the boot there is a large battery, which is recharged by the petrol engine and, when you slow down, by the momentum of the car. Its electronic brain decides which combination of engines should be used at any particular time.

An electric engine delivers huge torque from standstill, so the car usually starts with just the electric one. A petrol engine is inefficient at low speeds but has the advantage of ready availability of fuel and can be tuned to run efficiently at a mid-range speed. So it runs most of the time, but so quietly you can hardly hear it.

At very low speeds the Prius is an electric car - you can drive it as one for a mile or so before the batteries run down to a level at which the brain decides that the engine ought to start recharging them. When you are parking you just flick a little level up or down for reverse or forward and the whole process is done silently on the electric engine. Somewhere between 5mph and 20mph the petrol motor cuts in. On the motorway the petrol engine does the work, but the electric one will cut in to add oomph for overtaking.

I found it hugely satisfying to drive. Around town it is so quiet it is almost eerie. The engine cuts out as you approach the lights and you glide away in total silence. There is also the satisfaction of knowing that it is not wasting petrol or polluting the atmosphere. The worst fuel consumption I managed to get was 53mpg in the middle of London. The best? Not quite the 65mpg it is officially supposed to deliver, but 59mpg in the hills of Galloway.

Well, it is wonderful: roomy for four and acceptable for five, exceptionally quiet, plenty of power, squats down nicely on turns, has steering that tightens at speed - relaxing in every way. It is a nice, quality car, like the similarly-priced Avensis.

The most attractive quality is the elegance of the engineering. You are buying what is, arguably, the most advanced car in the world, but the design has been fine-tuned to fit form to function.

I suppose the only worry is that there is too much technology: everything is electronic, including control of the brakes. The idea that gears, steering, brakes and traction are all dependent on some electric circuit and a computer brain seems a bit disturbing. Were it anyone other than Toyota that had built the Prius I, would worry about reliability. As it is, anyone thinking of buying an £18,000 family car ought to get a test drive in a Prius first.

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