When you have a reputation for being the best, it becomes increasingly difficult to raise standards and you become the focus for the opposition to knock you off the top spot.

However, Mercedes-Benz has taken a pre-emptive strike against most of its opposition by freshening up the S-class.

Unlike the radical styling changes of the latest BMW 7-series, Mercedes has made some subtle alterations to the S-class, with more significant changes under the skin. It comes ahead of the launch of the Volkswagen Phaeton and Audi A8, and Jaguar is only just ready to show its latest XJ saloon at next week's Paris Motor Show.

But significantly for the British contender, it didn't event get a mention when Mercedes-Benz executives were explaining the virtues of the S-class compared with its rivals.

While the entry-level car – if it can be called that – remains substantially the same as the S280, all models now come with standard COMAND satellite navigation and a revolutionary new safety system called PRE-SAFE.

PRE-SAFE uses the car's electronic stabilisation programme (ESP) and braking assistance programme sensors to activate the seatbelt pre-tensioners, close the electric sunroof and reposition the passenger seats to better protect the occupants in a crash. If no accident occurs the system resets itself, and media representatives were treated to a demonstration at Mercedes-Benz's Offenburg test facility on the launch event.

Meanwhile, the S320 has been replaced by the S350, which has a new 3.7-litre engine, and the S320 CDI – which became the first diesel luxury saloon in the UK two years ago – gains a more economical and tax-friendly version of the engine, with second generation common rail injection and a power boost.

At the top of the tree sits the S600 L (only long wheelbase versions will come to the UK), with a new 5.5-litre twin-turbo V12 from the Maybach, developing 493bhp and a mind-boggling 590lb-ft of torque.

It will be sold alongside the new S55 AMG, which also boasts 493bhp, and although it has less pulling power than the V12, it makes up for it with a V8 roar more commonly found on a race track.

Professor Jurgen Hubbert, DaimlerChrysler board member for Mercedes-Benz cars, said: 'We are confident this car will master the challenges ahead of it. Introducing it four years after the current S-class was launched is in line with our product planning and we are very satisfied with the success this model has achieved.

'We have sold 307,000 S-class models worldwide since September 1998, and the volumes this sixth-generation S-class has achieved in four years has broken all previous records.'

The UK accounts for 10% of all S-class models sold, despite not being offered as the complete range (there is an S400 CDI and a short wheelbase S600, and now in mainland Europe petrol models will be offered with optional four-wheel drive), and the S-class has long been the market leader in the luxury car sector.

This is reflected in its strong residual values, with the smaller-engined variants easily retaining more than 40% of their value over three-years/ 60,000-miles.

It is significantly better than the equivalent model in the new 7-series and is predictably better than the current Audi A8. We expect the new A8 will offer an improvement over the current model and what analysts predict for the Phaeton next year is anyone's guess.

However, the S-class is likely to strengthen its position with the latest changes. CAP national research manager Martin Ward said: 'The best in its class just got better.'

Behind the wheel

WITH more than half the S-classes sold in the UK as diesels, it was important to get behind the wheel of the revised S320 CDI and put in some serious motorway miles. Although it isn't as powerful as the soon-to-be introduced BMW 730d – to which it gives away about 16 horses – it matches its rival on torque, and surpasses it on fuel economy and emissions.

The car starts with an absence of traditional diesel 'clatter' and settles down into such a distant hum, you wonder whether it is switched on.

With more torque than all but the S55 AMG and S600, the CDI will surge forward with indecent haste when required, and the auto box makes town driving light work.

A spell in the new S350 showed the new petrol engine to be remarkably refined, silent under all but the harshest acceleration. The 3.7-litre unit is more economical than the 3.2- litre it replaces, although the engine still puts the car in the highest band for company car tax.

The impact of the exterior changes is limited, with a change to clear-lens headlamps at the front and different rear light clusters. Inside, the dashboard is now in line with the new E-class and the switchgear has been changed accordingly. But the options list now contains new materials for interior trim, including nappa and nubuck leather in the designo couture package, while the seat upholstery has also been improved.

The range-topping S600 is a remarkable piece of machinery. Deploying its hefty 590lb-ft of torque must be troublesome even for the best transmissions in the world, and kicking down from fourth or fifth gear to second can come with an un-Mercedes-like jerk. It can be smoothed out if you use the manual shift facility, and when the lower gear is engaged, the S600 is ready for the jump to warp speed.

With the 0-62mph sprint dispatched in a supercar-like 4.8 seconds, accelerating in the S600 is a life-changing experience. The S600 also comes with standard dynamic seats which counter cornering forces by inflating the side cushions, as well as providing a relaxing massage as required.

Driving verdict

The S-class raises the stakes in the luxury car sector once again, with class-leading safety and refinement. The S320 CDI makes a convincing case for remaining in a company car instead of taking the cash alternative, while the S600 endows the Mercedes with supercar-like sprinting ability.

Mercedes S-class
Model	S350	S340	S500	S55 AMG	S600 L	S320 CDI
Engine (cc):	3,724	4,266	4,966	5,439	5,513	3,222
Max power (bhp/rpm):	242/5,700	275/5,750	302/5,600	493/6,100	493/5,000	201/4,200
Max torque (lb-ft/rpm):	258/3,000	295/3,000	339/2,700	516/2,750	590/1,800	369/1,800
Max speed (mph):	153	155	155	155	155	146
0-62mph (sec):	7.6	7.3	6.5	4.8	4.8	8.2
Fuel consumption (mpg):	25.6	24.7	23.9	21.4	19.2	36.9
CO2 emissions (g/km):	266	276	285	317	355	204
Transmission:	5-sp man
Fuel tank capacity (l/gal):	88/19.4
Service intervals (miles):	Variable under ASSYST
On sale:	October 1
Prices (OTR):	£44,410 (S280) - £87,580