Lexus RX

My favourite thing about the new Lexus RX 450h is not that it emits the least CO2 of any full-size SUV on the market thanks to its hybrid power train; it's not that it has a higher density of technology than anything else in the class; or that it can have an active anti-roll system for flatter cornering; it's not even that it looks much less like a turtle on wheels than its predecessor, although there is only so much the "assertive" new frontal design can disguise. It's the mouse.

Car-makers have tried many ways of enabling you to control the many parameters contained within a dashboard screen, be they SatNav, stereo system, car computer or air-conditioning. Buttons may be involved, or they may be dressed up as something clever such as BMW's iDrive with its giant, smoothly-acting knob. But you still have to turn and prod it to get what you want. It can drive you mad.

A computer uses a mouse, which gets straight to the point. And the Lexus RX 450h techno-hybrid has a mouse at the base of the centre console, a flat-topped joystick thing with a handrest with mouse-button on each side. You just select the menu, point the mouse where you want, click and carry on pointing as needed. If you think that's dangerous while driving, rest assured, the symbols are big, clever electronics suck the mouse arrow to the icon when it's close, and the system's mechanical damping makes it easy to use.

Is the rest of the Lexus as clever? Well, the usual official tests reward it with a CO2 count of 148g/km and 44.8mpg (the old RX 400h scored 192g/km), but these tests make every car seem more frugal than it really is. That so much taxation policy is based around these flawed figures should worry us, but the fact that a car of such low taxable emissions can produce 249bhp from its 3.5-litre petrol V6, plus enough power from its two electric motors to lift the possible tally to 299bhp, is an impressive achievement.

Two motors? There's one at the front, in a unit with the continuously variable transmission and able to produce up to 167bhp when the engine is producing little power or, as in traffic-crawling, is switched off. Another sits at the rear, able to contribute 68bhp and thus make the RX into a four-wheel drive car, albeit one with a significant frontward power bias.

The motors are similar to the old RX 400h's, but a new, smaller and more efficient power control unit and voltage converter allow them to work harder for longer. The battery pack is more compact, too.

As ever in a hybrid Lexus or Toyota, the interplay between electric and petrol modes is seamless and you can watch the energy flow on a real-time graphic. Or two of them: there's a small one in the instrument panel and a large, more detailed one as part of the main screen's repertoire.

Fine. So how does the RX 450h actually work as a car? It's a plushly and futuristically finished one, for sure. It's hard to tell if the orange-looking strips of wood are real, such is the gloss of the lacquer, but as you Lexuriate in your leather chairs you can't help admiring the precision of the switch design and the crispness of the instruments (including, optionally, a head-up display showing speed, Sat- Nav instructions and more).

There are three suspension variations: normal coil springs, the same with active anti-roll bars which twist the bars electronically to keep the Lexus more level in a corner, and air suspension which gives maximum calmness but also feels the most vague to the driver, like an old-school American SUV. Active anti-roll makes for a complete contrast, with positive steering and impressive agility at the expense of some fidgeting on lumpy roads. Which means the standard, simple version is actually the best; it's comfortable enough, it's responsive to the driver's commands and it feels the most natural.

All are much better than the old RX 400h, which used to feel jittery in the back and whose steering tugged this way and that under brisk acceleration.

So, if you need a hefty SUV and you're concerned about the tax bills, the RX is your car. Indeed, Lexus isn't even going to bother selling non- hybrid RXs in the United Kingdom.

It's priced competitively against diesel rivals, too. It costs from £41,600 to £55,505 and is on sale now.

Two electric motors and associated paraphernalia seems a lot of baggage to haul around, but the figures are compelling. Even better, it doesn't look so much like a turtle any more.