WHEN Jaguar announced it was embracing diesel technology for S-Type a few years ago I winced. And when it declared it was introducing it to its prestigious, best-selling S-Type I winced even more.

I quickly changed my mind after the test drive. The 2.6 litre V6 twin turbo engine developed from a PSA (Peugeot and Citroen) unit turned out to be the quietest, smoothest of the genre I had then driven.

The engine continues, along with the existing 3.0 and 4.2 litre petrol units in the latest manifestation of S-Type.

All of the new models are distinguished by the R model bumper and mesh grille and also new alloy wheels of 17, 18 and 19in.

The formerly limited edition XS model has now entered the mainstream, replacing the Sport but with additional styling features.

Inside the new cars, the seats have been made more comfortable.

At entry level, called Spirit, six-speed automatic transmission, leather seats and a leather clad steering wheel are standard along with rear parking sensors. The other specifications are called XS, SE and R.

Prices range from £28,995 to £45,000 and both lead-in and top end figures are lower than before.

The Sprit diesel driven on test in Monaco and its environs costs £29,995.

Jaguar adopted the diesel concept as part of its European go-forward - interest in the fuel in its principal overseas market, the United States, is miniscule.

It went without saying that the basic diesel design of the oil-burner just had to be good to justify the expense of its development and production at parent company Ford's Dagenham plant.

From Monaco I took the executive saloon through the always-crowded Riviera resorts and squeezed it through the narrow streets of countless sleepy villages. I then took the car up into the Maritime Alps, where the rain became torrential, and pushed it hard along the autoroutes that criss-cross the vine-covered lowlands.

The 206hp diesel is capable of propelling the car to 60mph from standing in just over 8s and beyond 140mph. It's fast - and it's also flexible.

More than 80 per cent of the car's 320ft lb of pulling power is available from 1,500 to 4,000 revs which beats even the 4.2 petrol unit. Aggressive yes - but docile in manners and easier on both the wallet and the planet. It can improve the latter car's fuel consumption by almost 50 per cent.

The going's great and the stopping's stunning thanks to the ABS braking system with supportive technology.

And you also get an electronic parking brake that keeps you steady on the hill starts.

The steering and the suspension were both modified a couple of years ago.

Since its re-styling, the S-Type gives the impression of leaping forward, as it should, rather than backwards. The panel fit is excellent and the bonnet is made of aluminium to reduce weight.

Adaptive cruise control is standard.