Based on the SW estate, the RXH has four-wheel drive as standard and uses a version of the hybrid system in the smaller 3008 Hybrid4.
A 2.0-litre turbodiesel engine sends up to 161bhp to the front wheels, while a 36bhp electric motor can drive the rears.
The RXH is easy to tell apart from lesser versions of the 508 SW. As well as a higher ride height, it has SUV-style body cladding, LED lights, bespoke, 18-inch alloys and a redesigned front bumper and grille.
A hybrid 508 saloon variant with more conventional styling will follow in the summer.
What's it like to drive? There are four driving modes ZEV, Four-Wheel-Drive, Sport and Auto.
Select ZEV (zero emission vehicle) and, as long as the batteries have sufficient charge and you're easy on the accelerator, the electric motor can power the car on its own for up to 2.5 miles.
Four-Wheel-Drive makes the two power sources work together to boost traction, while Sport sharpens the throttle responses and speeds up shifts from the robotised manual gearbox to maximise acceleration.
Alternatively, you can just leave the car in the Auto setting and let it decide for itself how best to optimise fuel economy and performance.
Whichever setting you choose, the drivetrain impresses; it switches seamlessly between diesel and electric power, plus the engine is strong. True, it gets boomy and transmits vibrations into the cabin under hard acceleration, but it's quiet and smooth at a steady cruise.
As a bonus, the linear surge from the electric motor helps the gearbox shift more smoothly than it does in conventionally powered Peugeots, although it's still slow and clunky compared with a dual clutch 'box or a conventional auto.
The rest of the driving experience could also be better. Even on the smooth French roads of our test route, the ride felt unsettled at all speeds, and while body roll is decently controlled, the steering inspires little confidence because it's inconsistently weighted.
Laminated side windows boost refinement. However, you still hear some wind noise from around the panoramic glass roof (a standard feature) and the suspension tends to clonk over bumps.
What's it like inside? Aside from a couple of readouts that show you how the hybrid system is working, and a dial on the centre console that gives you access to the different driving modes, the RXH is much like any other 508 from behind the wheel.
The dashboard is smartly styled and made from quality materials, although there are lots of buttons, so it can be difficult to find the one you want at a glance.
It's easy to get comfortable, despite an unusual driving position where your legs are stretched out in front of you. What's more, six-footers will have enough space in both the front and rear of the car.
Only the boot is compromised by the hybrid drivetrain; the floor has to be higher than it is in the regular 508 SW to accommodate the electric motor beneath, so capacity drops by 89 litres to 423 litres. The rival Audi A4 Allroad offers more than that, let alone big family estates such as the Ford Mondeo.
The rear seats can be lowered from the boot, but they don't lay completely flat.
Should I buy one? With prices starting at 33,695, the RXH is a seriously expensive 508 that makes little sense as a private buy. Instead, it's as a company car that it starts to look appealing.
It emits just 107g/km of CO2 and is exempt from the 3% penalty that usually applies to diesels, so will qualify for the 12% tax band when it goes on sale in May.
As a result, it will cost you less in company car tax than conventional 2.0-litre diesel estates that are as much as 10K cheaper, let alone the similarly priced and styled Audi A4 Allroad.
The fact that the 508 RXH averages almost 70mpg and comes generously equipped only adds to its appeal. We just wish it had a better gearbox and a more comfortable ride.
What Car? says...