Back-to-back: BMW 7 Series 730Ld vs Mercedes S-Class S350d L

Whenever a new luxury car comes along, it has one goal: to beat the S-Class.

The new 7 Series looks to have the best chance so far of ousting The Director. So it should – it’s the most modern rival Merc has yet faced, after all.

Testing cars like this is a bit different to normal, because much of the time their owners will be larging it in the back while Jeeves works for his living. Both our testers are the long-wheelbase limo models, which are designed with that in mind.

Behind the wheel, both 3.0-litre turbo-diesel engines are smooth, quiet and reassuringly powerful. Both have exactly the same amount of torque, but the BMW has a few more horses – as well as a superior auto box, which allows the 7 Series to accelerate usefully quicker.

That’s for what it’s worth, but refinement certainly does matter here and the S-Class has more of it. Both are excellent, but the reigning champ is a little quieter on the motorway and does a better job of damping out the patter from bad road surfaces around town.

The Merc’s steering is more communicative, too, should you venture into the sort of territory that counts as fun. Our 7 Series stayed flatter in corners, however – though that may have been the work of the four-wheel steer and active anti-roll bars which between them would have added £3500-ish to the car’s price.

Talking of options, both our test cars were fitted with rear-seat upgrades including an entertainment system, premium ICE and massage and recline functions for the seats themselves. These were priced at £4815 on the 7 Series and £3500 on the S-Class.

Naturally, you get stacks of kit as standard, and all of it’s top-notch stuff. Soft leather, classy trim, ambient lighting, good wi-fi and so on – people buy these because they want to be looked after.

And they keep going back to Mercedes because they know they will be.

BMW’s task is to get more of them coming its way, and the 7 Series will do that. But while there’s no objective way of separating one interior from another here, the S-Class has an indefinable something that’s still untouched. Details you don’t even notice make the difference at this level, and Merc remains on the highest level of all.

Be under no illusions, though. If you were to sit in a 7 Series without trying any other vehicle, you’d instantly assume that nothing else could come close. It’s that good.

But if you were to sit in both, we think you’d come to the same conclusion as us. Because the S-Class really is THAT good.

It’s cheaper to own, too, when everything is taken into consideration (discounts and residuals swing it, though the taxman does his best to get you into the cleaner BMW). The likely saving is something like £7000 over three years, however, and you probably earn that every week if you’re in the market for one of these.

So the money wouldn’t swing it if the better car was more expensive to own. As it is, though, the S-Class makes more sense in terms of ownership – which just backs up our conclusion that brilliant though the 7 Series is, The Director has seen off this latest attempt at a boardroom coup.

Engine size: 3.0-litre diesel, turbo

Price from: £67,995 (list)

Power: 255bhp

Torque: 457lb ft

0-62mph: 7.2 seconds

Top speed: 155mph

Fuel economy: 34.7mpg (on test)

CO2: 148g/km

Engine size: 3.0-litre diesel, turbo

Price from: £68,480 (list)

Power: 261bhp

Torque: 457lb ft

0-60mph: 6.3 seconds

Top speed: 155mph

Fuel economy: 58.9mpg (govt)

CO2: 127g/km