Lexus LS shows big can be green - On the road

Although it's closely related to the LS460, most of the LS600h's internal workings are different to accommodate the hybrid powertrain.

For a start, the V8 petrol engine is bigger, at 5.0 litres, and it combines with an electric motor to give 439bhp. That's enough to make it seriously quick, but the LS600h's 'green' credentials are equally important.

Average fuel economy of 30.4mpg isn't bad for such a big, powerful car and carbon dioxide emissions of 219 g/km are also low for its size and weight - one VED band lower than most big luxury cars. Both are a big improvement over the LS460, if not a Mercedes S320 CDI.

Many buyers are likely to experience life from the back seat and that's the best place to savour the LS's fabulous refinement. Yet life is good in the driver's seat, too. You're aware that it's a big, heavy car, but the 600h is easy to drive and the ride quality and CVT (continuously variable transmission) gearbox are smooth.

In stop-start city traffic the car runs on electric power only and is almost silent; when the petrol engine kicks into life, it does so smoothly and quietly. As with most hybrids, there's a whirring noise and rather abrupt action when you brake hard, as the electric motor boosts stopping power and charges the battery, but it doesn't spoil the drive.