| First Drive | Stuttgart, Germany | Future Mercedes-Benz S-Class |

In September we drove the latest incarnation of Mercedes' S-Class with updated engines. Little over a month on and we've muscled our way behind the wheel of what could, and probably will be, the next phase in Merc's flagship luxury car. The next S-Class is due in 2013 and throughout its lifetime we can expect to see the arrival of a plug-in hybrid version that can drive completely by itself at low speeds.

In the Metal

We can't comment on the looks of the next S-Class just yet, as the two prototype cars that we drove were for technology purposes only, so they were both wearing current S-Class bodies.

We did, however, bag a ride in the sleek F800 concept car, which was unveiled at this year's Geneva Motor Show and has the same plug-in hybrid system as the future S-Class will - give or take a few tweaks before production. With that in mind, it's reasonable to speculate that the next S may take on a few of the F800's finer features. That's a very good thing.

What you get for your Money

Again putting a price on it is nigh-on impossible at this stage, but it's worth mentioning exactly what technology Mercedes is planning to include. The plug-in hybrid system features a 300bhp V6 petrol engine mated to an 80kW (about 107bhp) electric motor. It can comfortably travel on electric power alone at speeds of up to 75mph with a 19-mile range. The petrol engine kicks in to offer extra power when you need it and when both are working together they can muster as much potency as a traditional V8 petrol engine.

As for a car that can drive itself, that's courtesy of the latest incarnation of Mercedes' Distronic adaptive cruise control system. The current S-Class can avoid a nasty collision by automatically applying the brakes and pre-tensing the seat belts before an impending shunt, but the next generation takes this one step further and automatically accelerates, brakes and steers the car when following other traffic at low speed. It works at a range of up to 30 metres and only within a specific carriageway lane, so theoretically there's no danger of the car following a swerving driver who's had one too many.

Driving it

The plug-in hybrid S-Class - referred to as 'Premium Plug-in' by Merc's engineers - is certainly the more impressive of the two technologies. Like other serious hybrids and electric cars, it's silent at low speed and emits only an eerie, high-pitched hum.

Unlike most cars of its ilk, the S-Class keeps running on electric power. We're used to cars such as the Toyota Prius that run for a very a short amount of time at low speeds on electricity, but this one is different. For the length of our short test, it happily remained on electric power alone unless we really put the boot down. Mercedes says that the V6 engine kicks in when the driver depresses the accelerator pedal by 90 percent or more, which we would testify to. The transmission between engine and motor is quite jerky, but that's not unusual for a pre-production model.

The self-driving S-Class is undeniably clever, but not quite there yet. To activate the Distronic system, you nudge the cruise control lever upwards, gently tap the throttle and the car smoothly follows the vehicle in front of it. The system cut out once or twice while we were using it and it requires the driver's hands to be on the wheel for a certain amount of time in order to remain active, so it's not quite as polished as it could be. We're in no doubt that Merc will get it right sooner or later, but the practical application is questionable.

Worth Noting

The next S-Class is due to go on sale in 2013 but these features won't be available from launch. The plug-in hybrid is all but ready to go; however, as we mentioned, the next generation of Distronic isn't quite there yet. Mercedes hasn't confirmed when either system will appear on the options list, but our money is on around 2014 for the plug-in hybrid. Distronic is currently anyone's guess, but it's reasonable to assume that it will arrive later on.

Summary

We're all for the Mercedes-Benz S-Class plug-in hybrid. A proper luxury car that can run on electricity alone at real speed and distance is a great breakthrough - especially when it retains the potency of a V8 engine. Great stuff. We're less in favour of the Distronic, though. It's undeniably clever and futuristic, but should drivers really need a car to drive for them in heavy traffic, or should they be paying attention? We'll certainly find out in the next decade.