With a transversely-mounted 246bhp 3.5-litre petrol V6 supported by two electric motors working in tandem for ‘intelligent 4WD capability', power is boosted to a total of 295bhp, or plus 10 per cent on the outgoing 400h. Peak torque isn't quoted, but if you add the V6's 317Nm to the front electric motor's 335Nm and the rear electric motor's 139Nm (both AC synchronous) then you'll realise that there's no shortage of useful urge.
On the road, and assisted by its electronically-controlled Constantly Variable Transmission - no rubber bands here, instead a wonderfully engineered planetary gear system - the new RX has all the overtaking prowess you could wish for from an SUV. Although its quoted max of 124mph isn't exactly inter-galactic, the 450h can very comfortably maintain jail-sentence speeds on the motorway, should you so choose. And, with a circa 2.2 tonne kerb weight, the 0-62mph time of 7.8 seconds is impressive, too.
Regarding the CVT, I should mention that when throttle is applied the engine revs rise and fall much as they do on a 50cc scooter. Some may find this trait not in keeping with a luxury vehicle, but the upside is that it's always in the right gear, or more accurately, continually employing the correct ratio, and so is more efficient than a conventional torque-converter auto.
Arguably more impressive are the new RX's official fuel and CO2 figures at 44.8mpg (combined) and 148g/km. Driven carefully, as distinct from ‘slowly', 50mpg or more shouldn't be impossible to achieve, but if driven like there's no tomorrow then you'll see little if any improvement over other big, petrol-powered Chelsea tractors. That said, the new RX's CO2 output is, for example, officially 98g/kms lower than a Mercedes ML320 CDi SE's, and so places it into the new Band F VED rating, or a relatively paltry £105 per year road tax. Find another 300-horse SUV that can approach those numbers and it definitely won't be 2009 any more…
Other significant updates to the 450h include three new driving modes: ‘ECO' (eco mode in hybrid), ‘EV' (electric only - range 3km) and ‘SNOW' (you guessed correctly), plus a class-leading 0.32 drag coefficient and even more sophisticated Pre-Crash Safety, Adaptive (radar) Cruise Control and Vehicle Dynamics Integrated Management systems.
There's also a new double wishbone rear suspension system, which, apart from allowing a small increase in rear boot space, is what classy sports cars have and is therefore better. That's the theory, but in practice this RX's ride quality can fall way short of what we might have expected of any Lexus bar the overtly racy IS-F.
The new RX employs three different suspension systems, depending on model. The base SE version rides on conventional coil springs, the SE-I employs springs with an Active Stabiliser System, while the top-spec SE-L versions glide along on electronically-controlled air suspension plus the Active Stabilisers. I didn't get to drive a coil-only equipped SE, so can't comment on that, but the active stabilisers limit body-roll noticeably while cornering. Trouble is, on anything but a billiard table-smooth surface, the SE-I's coil-sprung ride quality is uncomfortably choppy and entirely out of character with the brand. Fortunately, the £5,210 more expensive SE-L air suspension offers salvation and I'd not be content with anything less.