Power, speed, handling – those are the attributes on which Jaguar traditionally built its reputation as a quality car manufacturer.

Now, with the arrival of the Coventry company’s most efficient engine yet, the word economy has been added to that lexicon.

The new 2.2 litre four-cylinder diesel currently testing on UK roads is capable of returning an impressive 52.3 mpg fuel consumption figure in the combined cycle, with commendably low carbon emissions.

Features include a water-cooled turbo-charger with low-friction pistons, new injectors and a new crankshaft while the engine is installed in a north-south configuration for he first time to facilitate the fitting of a super-intelligent stop/start system that improves fuel efficiency for an estimated five to seven per cent.

Also featured is an advanced eight-speed ZF automatic gearbox. With the seventh and eighth gears effectively operating as overdrive ratios, this unit enables super swift responses and an ideal balance between performance and economy. The 0-62mph sprint takes 8.5 seconds on the way to a maximum 140 mph.

But if performance is your prime desire, cast your eyes instead over the impressive £49,950 3.0-litre diesel S Portfolio that I drove for a busy week of mixed motoring,

It's a formidable challenger in the luxury performance saloon sector, a market that has been dominated in recent times by the German triumvirate of Mercedes, BMW and Audi, with Lexus nibbling away for a market share.

Cynics may argue that recent Jaguars have been Ford Mondeos in big cat clothing but I’d counter that the XF has an upmarket character that’s far removed from humble underpinnings.

The bigger engine can whisk the XF to 62 mph in just 5.9 seconds, making it quicker off the mark than many of today’s pure sportscars. More importantly for safely driving quickly, 50 to 70 mph takes a mere 3.2 seconds, ensuring safe overtaking. Top speed is an electronically limited 155 mph yet this big saloon can achieve 44.8 mpg when driven more gingerly.

Ride and comfort levels are high, though getting in and out can be s bit of a squeeze for larger, long-legged drivers

Equipment levels are comprehensively high, with a whole raft of goodies, from gearing with winter and dynamic modes to cruise control and speed limiter, bi-function HiD headlamps that switch automatically from full-beam to dip mode when there are approaching vehicles; a smart key system and an electronic parking brake. There’s even the option of a heated steering wheel.

As have always been handsome beasts and the svelte XF is no exception though some might feel the transatlantic styling influence is a tad too strong.

The big cats also enjoy a long-standing reputation for providing a great driving experience and here too the XF is a winner. Just as importantly for this kind of car, passengers – whether front or rear seated – are truly cosseted in a superbly plush and well-appointed cabin