The hybrid-only Lexus RX450h is a large SUV that competes with the BMW X5, Mercedes ML-Class and Audi Q7. By combining a 3.5-litre V6 engine with a pair of electric motor is manages to return 44.8mpg, but thanks to a combined power output of 295bhp it has a surprising turn of pace too. The RX450h is at its best at cruising speeds, when refinement and comfort is superb - in the corners though it loses out to more dynamic rivals. Loading space is slightly less than its rivals, but a flexible interior layout makes the most what's there, so it should prove adequate for even a large family.

The RX was the first premium hybrid 4x4 to arrive in the UK and the latest model calls upon a 3.5-litre V6 and two electric motors – one at each axle – to provide the power. In a straight line the RX is quick, with 0-62mph dispatched in 7.8 seconds thanks to the 295bhp output. Yet, show the RX a few bends and it starts to show its size. There's dramatic understeer if you carry too much speed into a bend and torque steer when you get back on the throttle as the four-wheel drive system is quite slow to react to a loss of grip and there is no central driveshaft as the rear-mounted electric motor drives them. Refinement is excellent however with very little wind, road and engine noise making its way into the cabin, so long journeys are a breeze. An electric-only mode can be accessed at low speeds, which makes driving through towns a relaxing experience, too. You can travel up to one mile in EV mode and in everyday driving it doesn’t take too long for the battery to fully recharge, so it’s more useable than you may think.

Compared to the previous model Lexus has managed to boost power by 10 per cent but cut CO2 emissions and fuel consumption, by 23 and 28 per cent respectively. Lexus' official figures are 44.8mpg and 145g/km, significantly better than a BMW X5 30d, but in the real world you'll struggle to match them on anything except short journeys around town. In our test, which included A-roads, B-roads and city driving, we only managed 27mpg. The purchase price is also very high - you can have a Land Rover Discovery or Audi Q7 for less - but residual values are good. Still the extra cost of the expensive hybrid drivetrain will be a lot to stomach for some buyers.

Recently facelifted, the Lexus RX 450h now features the same pinched grille as the all-new GS - and Lexus claims it's a feature we'll be seeing more of on future models. The overall proportions are similar to the original RX - launched in 1998 - so it doesn't have the same road presence as its closest rivals - the BMW X5 and Mercedes M-Class. For extra visual impact there's an F Sport model, which features dark alloys, tinted light clusters and a chunkier body kit. On the inside the sweeping dash is dramatic, although the expanses of wood trim won't be to all tastes. There's no denying the quality of the materials used are first rate though and standard kit, which includes sat-nav, heated and electrically adjustable leather seats and a Bluetooth phone connection, is very generous indeed.

Lexus has also just launched an Advance trim, which takes the sportier exterior styling from the F-Sport model but adds a full panoramic roof, LED headlights and 19-inch alloy wheels.

Unlike most hybrids, the RX 450h's battery pack doesn't encroach on the boot space. The result is a 496-litre boot, which is still someway down on the BMW X5, and even smaller still than the smaller BMW X3. The rear seats also fold, slide and tilt independently of one another, so you can maximise boot or passenger space to suit particular needs. The fact that there is no central driveshaft also means the footwell floor is totally flat - making it easier to carry five adults in comfort than it is in conventional 4x4s.

Build quality and reliability have always been cornerstones of Lexus' success, with it regularly topping the customer satisfaction tables in our Driver Power survey. Ten airbags a sophisticated stability control system all come as standard, as does radar cruise control, which regulates the distance between you and the car in front, and a pre-crash safety system that prepares the car if it senses an impact is imminent.