WHEN Jaguar launched the XF at the beginning of last year it marked a dramatic change of direction for the Midland car company, both in terms of design and innovation.
The new car won critical acclaim all over the world, with the 2.7-litre diesel - the best selling model - singled out for its performance, economy and driver enjoyment.
Since then that engine has been replaced by a 3.0-litre turbo-diesel unit and with this comes the real icing on the cake - the XF Diesel S.
Buying one compared to buying a standard diesel XF is like buying a MINI Cooper S rather than a MINI Cooper. It might look almost identical but when you get behind the wheel the difference is immediately apparent.
The S boasts 275bhp compared with 240 for the standard 3.0-litre engine and is a staggering 33 per cent more powerful than the original 2.7-litre engine - a power unit we all raved about when we first drove the XF diesel - and has 61 percent more torque from 1,500rpm.
On the road it's sheer poetry in motion. It has everything anyone could want from a large diesel saloon in a comfortable, refined yet sporting package.
The car will reach 60mph in just 5.9 seconds but the really impressive performance comes with its mid range power delivery. When you accelerate hard the second of the twin turbos comes into play and the XF leaps into action at a phenomenal rate. Not too long ago this sort of performance would only have come from a car with a V8 under the bonnet.
The XF S jumps from 50mph to 70mph in just 3.2 seconds on its way to its maximum speed of 155mph.
And the bonus is Jaguar claims it will average 42mpg, although in my experience on the road that figure was usually around the high 30s mpg mark, which for this size of engine and weight of car is still nothing to be sniffed at.
The economy is achieved because for most day-to-day driving, including motorway cruising, the variable-geometry primary turbocharger does all the work, while the smaller, secondary turbo is dormant, saving energy and improving efficiency.
It's only when you need real performance and raise the revs above 2,800rpm, that the secondary turbo is brought on line - within 300 milliseconds - giving that dynamic performance which sets this car apart.
With this engine Jaguar has raised the bar both in terms of diesel performance and diesel refinement.
And along with performance comes exemplary handling. The road holding and ride are superb no matter how much you push the car and the steering is precise, pin sharp and a joy to use. It is certainly car which sets new standards and is the benchmark to beat.
Diesel engines of this quality used to be the preserve of German manufacturers but it's Jaguar which is now leading the way with this home-grown version.
This sportier version of the XF is distinguished by 19 inch wheels, an aerodynamic boot lid spoiler and discreet 'S' badging, so in true Jaguar style you can have a car which has all the power and performance you will ever need without having to flaunt it too much.
FAST FACTS
Jaguar XF 3.0 V6 Diesel S Portfolio
Price: £44,200
Mechanical: 275bhp, 2,993cc, 6cyl diesel engine driving rear wheels via 6-speed automatic gearbox
Max speed: 155mph
0-62mph: 6.4 seconds
Combined mpg: 42
Insurance group: 18
C02 emissions: 179g/km
BIK rating: 21%
Warranty: 3yrs/ unlimited mileage