I’ve never been a fan of the Toyota Prius. While I admire the success with which the petrol-electric hybrid has been marketed to Hollywood A-listers and environmental show-offs, as a product it’s been about as convincing as a chocolate oven. Not only is it expensive, and tedious to drive, its environmental credentials are enough to turn greens red-faced.

If you really want a car with emissions of 104g/km, why not save a fortune and buy a Mini Cooper D, which will not only cost thousands less, but will be as fun as the Prius is dull, and will use less fuel to boot. And if you need more space, get the Clubman version. It’s only in places such as America and Japan, where diesel is a dirty word, that the Prius has made any sense.

Until now. The third-generation Prius may not look that different from the car it replaces but it has been redesigned from the floor up. More powerful yet less thirsty, more environmentally considerate but no longer actively discouraging to drive, it feels like the car the Prius should have been from the start.

Its basic concept is unchanged. There is no revolutionary technology such as lithium-ion batteries, which will undoubtedly transform hybrids when their cost can be brought under control. As before, drive comes from a petrol engine, but it has grown in capacity from 1.5 to 1.8 litres, and yet is more frugal. This is boosted by an electric motor powered by old-tech nickel-metal hydride batteries, although these are claimed to be more efficient than before, and the electric motor is smaller, lighter, yet more powerful.

At last there is no arguing with the figures. No other car on sale can match the CO2 emissions of the new Prius, of just 89g/km, while Toyota says it will do 72.4mpg — not only on the combined cycle, but around town too.

The power increase from 112bhp to 134bhp is noticeable, and brings the 0-62mph time close to single figures. This performance gain is thanks in part to the bigger engine. The Prius has to date attracted criticism for its thirst, especially out of town, but the bigger engine doesn’t have to work as hard at a steady cruise, and so uses less fuel.

The new Prius now offers a perfectly acceptable means of getting from A to B in comfort. The cabin is more spacious, particularly in the back where legroom has been improved. The ride is cushioned yet controlled and no longer has the car feeling as if it’s falling over in corners: in fact the handling can now be described as thoroughly competent.

But you still have to adapt to driving a Prius. Take the gearbox, for example. It is of the continuously variable (CVT) type, which is more efficient than a conventional manual or automatic. I have been driving cars with CVT gearboxes for more than 20 years and am yet to find one I like. And this Prius does nothing to change that.

To really enjoy the Prius you have to be an “early adopter” — a lover of all things technical. Toyota has spent years perfecting its Hybrid Synergy Drive and wants you to know it: a display in the dashboard provides a bewildering array of information about how you are driving, how you should be driving and how to improve, so one day you’ll go to green heaven. There are even settings tailored to drive for economy, performance or purely on electric power. This last mode is available only at town speeds, and rarely for more than a mile or so, but it remains fun and relaxing to waft your saintly way in complete silence.

Despite such improvements, it’s not difficult to see where Toyota has cut costs. The most popular model will be the range-topping T-Spirit with a list price of £21,210, yet its cabin is plastered in cheap, hard plastic.

Even if this new Prius is intermittently annoying, it no longer makes you want to drive it off a cliff. On the contrary, what once felt like a technology testbed shaped like a car now feels like a car with increasingly convincing technology. In tacit acknowledgment of how overpriced the outgoing Prius was, the new entry-level T3 and flagship T-Spirit won’t cost a penny more than the models they replace — despite the extra equipment and new technology.

The UK market for this car is small and shrinking; Toyota reckons it will sell fewer of this new Prius next year than it did the old one last year. Despite so many improvements, you can see why: people are downsizing, the Prius still seems expensive and there is no shortage of credible diesel-powered alternatives. Even so, what could make it a surprising success is that it has managed to hang on to its environmental credentials while becoming a whole lot easier to drive and live with.