The outgoing car had been offered in certain markets as the S250 CDI, featuring a 2.1-litre four-cylinder diesel with CO2 emissions of 149g/km. But this will not be directly replaced in the new car.

'When we introduced the S250 CDI we were aiming for best-in-class CO2 emissions,' an engineer told Fleet World. 'Now the diesel hybrid is able to achieve this comfortably.'

Using the same modular hybrid system as the E-Class, the S300 BlueTEC Hybrid combines a 2.1-litre diesel engine with a 27bhp electric motor, returning a class-leading 64.2mpg and CO2 emissions of 115g/km. 

The manufacturer has also invested heavily in further reducing NVH compared to the E-Class, to ensure that refinement isn't blunted for the only new S-Class to use a four-cylinder engine, the engineer explained. 

The UK has so far proved receptive to the carmaker's diesel hybrids, becoming the second largest market for the E-Class Hybrid after Germany. In both cases, sales have greatly exceeded expectations. 

Next year, the range will be augmented by the luxury sector's first plug-in hybrid. Full details will be announced at the Frankfurt Motor Show, but this will offer an extended fully electric range, recharged from a port in the back bumper and with fuel economy in excess of 70mpg on the NEDC's plug-in hybrid test cycle. 

The UK is predicted to be a key market for the S500 Plug-in Hybrid, where its sub-75g/km CO2 emissions are expected to make it popular in London, as it slips under the new congestion charge threshold and lowest 5% BiK band. 

However, the S350 BlueTEC, which uses a 3.0-litre six-cylinder diesel engine, is expected to be the volume seller in the UK. This offers CO2 emissions from 146g/km and a combined 51.4mpg. 

Sales of the new S-Class begin in July, available in a choice of long and short wheelbase versions and either SE Line or AMG Line trims. Prices start at £62,650 on the road.