With the move towards hybrid and electric power - plus the seemingly ongoing demonisation of diesel - who is going to buy a diesel version of the latest S-Class, I ask myself? I can only imagine the S400d L, as with previous generations of S-Class, is going to appeal to chauffeur companies, ferrying executives between customers' homes to airports around the country. This is where the 38.7mpg combined fuel figure and 670-mile range would undoubtably appeal. 

This is an expensive car and costs are high with the 37% BiK and £1.37 per mile, over three-years/60,000 miles, but for buyers it will not matter because of the brand.

However, to only look at the running costs of the S400 dL isn't really getting the point of the world's best-selling luxury car. Firstly, there's the history, which dates back six-generations, and has debuted many of Mercedes' latest innovations.

This S-Class is no different as it debuts the next generation of Mercedes-Benz User Experience (MBUX) with a 12.8in OLED touchscreen central display, a 12.3in digital driver display, plus an MBUX tablet (part of the Executive line trim) - which can be used as a fully-fledged tablet outside of the vehicle. The driver display is also available with 3D technology as an extra, which was fitted to our test car. We found it easy to use, but even after four-days behind the wheel, we'd only scratched the surface of its capabilities. Also, the 3D driver display takes some time to get used to - it made us feel a bit dizzy for the first couple of hours behind the wheel.

The S-Class has to have one of the nicest interiors we've been in. The screens float on a dashboard made of a large, polished piece of wood that stretches into the door cards. The 'floating' theme carries on to the door pulls and electric seat controls - which don't look fixed to the door. Then there are the front seats which are both comfortable and supportive. The 1,750W Burmeister sound system is top notch too.

The S400d is only available with the long-wheelbase body - this equals expansive rear legroom, plus more exceptionally comfortable seats. The boot is practically shaped and totals 540-litres. Refinement is exceptional too; this and the comfort should be more than enough to enjoy being driven rather than driving. 

Our range-topping AMG-Line Premium Plus Executive model rode on 21in wheels and big wheels are usually a cause for worry - but not with the S-Class. Air suspension, plus a full suite of technology keeps this Mercedes driving smoothly, even when you investigate its 330hp on a twisty road - not that many will do that. Considering its 2,090kg weight, the way this Mercedes behaves is more like a smaller saloon with half its weight. The steering is responsive, the body control is excellent, and the head-up display has all the information you need - without having to take your eyes off the road. 

Electric power and the EQS are incoming, but it will have to be even more impressive to topple the S-Class as one of the best luxury saloons.