Can a big beast have a small appetite? Can a rhino charge around the Serengeti plains all day, upsetting zebras and annoying wildebeest, and be happy with a small plate of cucumber sandwiches for tea?

These urgent zoological questions (and others) queue up in your mind as you settle yourself into the Lexus 450h for the first time. For this is a big, muscle-bound beast that will scare Skodas and bully BMWs – and yet its maker claims a mouse-like thirst of just 44mpg.

To find out how Lexus performs this conjuring trick, you need to head off into some unfamiliar technological territory. The orthodox bit here is the regular petrol-powered 245hp petrol V6 under the bonnet; what’s unexpected is the nearby 167hp electric motor that drives the front wheels.

Go to the back and you’ll find another electric motor, this one 68hp and powering the rear wheels. And under the back seats is a big nickel-metal hydride battery that can send its power to either (or both) electric motors.

Start the car up and there’s a deafening silence. Put the auto transmission into drive, dab the throttle and the Lexus starts to move off under electrical power. The only noise as you gather speed is a tiny whirr like a distant electric toothbrush.

Squeeze the throttle a little more and the engine decides to join the party. You can’t actually hear it start and the only clue comes from the groovy animated power meter (left) on the dash. The car remains in this mode as long as your foot is pressing the throttle. Ease off and the engine silently cuts out; stab the pedal and it re-starts. You’d expect some coughing and jerking as it comes in and out, but it’s as smooth and seamless as a David Cameron speech.

In fact, every time you slow down or brake, a generator puts power back into the battery, hence the car’s modest thirst. All of this happens in as civilised and confident a manner as an ambassador’s garden party. But floor the accelerator and both electric motors and the petrol engine join forces to give you a true get-out-of-my-way-plebs mode.

With a roar like a jet fighter, the 450h picks itself up and charges forward as if into battle. Passengers’ jaws drop, hands tighten on door grips. Nervous laughter breaks out in the back seats.

Take your foot off the throttle, though, and it all goes quiet and civilised again. The tinkle of conversation resumes and it’s as if nothing quite so shocking had happened.

All good fun, but the question is this – can a 2.7t vehicle go from 0-60mph in 7.8 seconds and its driver not become a depressingly regular visitor to his local petrol station?

The answer is maybe. All this fun and frolics meant I managed to get about 31mpg. Normal use (with less of that fighter-pilot stuff) would probably see it in the mid-30s mpg. Not quite the 44mpg quoted by the maker but a figure that drivers of other big 4x4s could surely only dream of.

So extraordinary is the Lexus’s hybrid drive that it almost eclipses the rest of the vehicle. But in almost all areas this is a plushmobile without flaws. The ride is as smooth and level-headed as you’ll find on an off-roader, though it’s a bit too sensitive to slow-speed lumps and bumps.

It’s comfortable and plush, with all the usual hi-tech play things. There’s even an electric tailgate opener/closer for those who find doing it by hand too arduous.

Summing up

A credible Range Rover rival, with a modest thirst. Expensive, but certainly worth robbing the bank for. Shame no one else has brought out a smaller hybrid 4×4.