Mercedes S400 Hybrid: Motoring review - Why do we care about a £70k car? One day, its gadgets will be ours...

Mercedes S400 Hybrid, from £69,650

PRICE: from £69,650
ENGINE CAPACITY: 3.5-litre petrol V6 (plus electric motor)
POWER OUTPUT (BHP @ rpm): 306 (27) @ 6,500
TOP SPEED (MPH): 155
FUEL ECONOMY (MPG): 44.8
CO2 EMISSIONS (g/km): 147

My passenger is asleep. She was my co-driver a few moments ago, helping me with navigation and providing witty anecdotes, but that didn't last. She'd been eyeing up the back seat and the first chance she got, she hopped out and into the back of my test Mercedes-Benz S-Class limousine. There, she promptly fell asleep, leaving me with nothing but Radio 4 for company.

Not that I blamed her. The S-Class is the German carmaker's flagship model and its rear gets everything from heated and massaging seats to a television screen and dual-zone climate control. Here's the conversation killer, though; the passenger-side rear seat reclines to a snooze-inducing 37 degrees, has a headrest more comfortable than a memory-foam pillow and, of course, a footrest for the tired executive's feet. My tired executive slept from the West Country back to west London, and that's exactly what Mercedes had hoped for.

The truth is the Executive Rear Package – I kid you not, that's its name – is actually a £3,510 option. That said, if I were the CEO of a German precision engineering firm, commuting (well, being driven) from Stuttgart to Frankfurt weekly, I'd insist on it. Unsurprisingly, the analogy doesn't work as well if you're commuting to work in Surrey or running up to Solihull.

Mercedes had offered me a chauffeur to test this out, but I declined for fear I could be putting myself out of this car-reviewing lark, and I actually wanted to drive it. Nonetheless, you might ask what relevance a £70k luxury saloon with a bed in the back has to you. But the gadgets and developments on cars such as the S-Class will be the standard features of tomorrow.

Tomorrow's drivers, then, will be pleased to hear that the S-Class is rather good. My solitary drive gave me plenty of time to test out its silky-smooth suspension and its innovative hybrid system, which is likely to make an appearance on more modest Mercedes models in the future. It's also one of the most seamless I've driven and brings the C02 emissions of this tank down to a more-than-acceptable level.

There is no escaping, however, just how unwieldy this 5.2m-long (17ft) beast is. All that space comes at price, and while it's fine on the motorway, it's a little tricky in your local Tesco car park. Then again, if you can afford one of these, you can afford the professional to drive it for you.