The puzzling thing about the new Jaguar is that we haven't seen it before now.
Maybe the notion of a four-cylinder car catches a raw nerve of brand-value betrayal among those wedded to the past. But the company has looked to the future in recent years, and not before time.
I drove one of the first cars to bear the Jaguar badge last year, a 1937 SS saloon with a 1,608cc engine. It, too, had four cylinders, but, unlike the new XF 2.2D, it was very slow – all style and no substance. Its descendant, by contrast, has both.
In between these two temporal extremes we have also had a couple of four-cylinder versions of the unloved X-Type, a car through whose heart a senior Jaguar executive once confided to me that he would like to drive a stake. Then there's the fact that over 80 per cent of new BMW 5-Series models sold are four-cylinder diesels with a 520d badge. Such engines are what the market needs in a large, prestigious saloon. They were needed in 2008, the year of the XF's launch, too, but not as desperately as now. For three years the XF has tried to stay a cut above its German rivals and not stoop to the plebeian depths of four-cylinder poverty models. But the world has changed and so has the XF. It has had a visual facelift, a little mechanical massaging – and the addition of this new, 2.2-litre turbodiesel option derived from the unit used in some Land Rovers, large Fords and family-sized Peugeots and Citroëns. The idea is that the sales floodgates will open, as all those company execs who coveted an XF but couldn't justify (or weren't allowed) a big-engined, high-tax, high-CO2 car can now sate their craving.
The new mood of engine-related parsimony does not mean the rest of the car has to suffer. The XF 2.2D comes in the same specifications as the V6 and V8 models: SE, Luxury, Premium Luxury and Portfolio, with prices from £30,950. Besides, the latest four-cylinder turbodiesels are marvellous things in their own right: smooth, quiet and able to deliver amazingly effortless thrust from low speeds to high ones.
In the Jaguar, the engine is mounted longitudinally instead of transversely, and it drives the rear wheels instead of the front ones via an automatic gearbox containing eight forward ratios. Power is 190bhp, torque is a monstrous 332lbft at just 2,000rpm, and you could hardly hope for a sweeter, quieter diesel. If you stand outside an idling XF 2.2D you can hear just a hint of a diesel's deep, slightly percussive thrum, but it's quiet and cultured. Inside, you can't hear the dieselness at all, just a distant, deep hum, which is rather restful.
All that easy, modern-diesel thrust is here in full measure, allowing this heavy car to surge easily to 62mph in 8.5 seconds. Its top speed is 140mph, but more relevant is that the long-legged eighth gear gives absurdly relaxed cruising. Just 1,600rpm shows on the rev-counter at 70mph, helping towards the low 149g/km CO2 figure.
The gearbox shifts quickly but smoothly, and there's a responsive manual mode triggered by paddles on the steering wheel – you can miss out gears by pulling on the paddles more than once as needed, which is useful when there are so many gears. And the stop-start system works sufficiently quickly and intuitively that you don't feel tempted to turn it off.
All fairly wonderful so far, then. It gets better. Because this is the smallest and lightest XF engine, it makes the car's front end lighter. And this makes this XF feel especially keen and agile on twisty roads or in town; it feels smaller than it is, but it retains the accurate, intuitive-feeling steering and marvellously gentle riding quality of the other XFs. This is where the Jaguar really scores over its German rivals, in its mix of suppleness and precision.
Other XF attributes remain, or are enhanced: the crisp interior with its unusual use of wood, the rotary gear-selector knob which rises out of the console on start-up. Outside, there's a bolder nose with a bigger grille, and LED running lights, plus reshaped side vents and new tail detailing.
Details aside, what is key is that this new XF, destined to outsell all other XF models combined, works beautifully. The best car in its class? Probably. The most desirable? Definitely.
Audi A6 2.0 TDI SE: £30,145, 177bhp, 129g/km
New A6 looks much like the old one but has impressive cabin electronics. The entry-level A6 is the nicest to drive of the whole range.
BMW 520d SE: £29,430, 184bhp, 129g/km
Not quite the "ultimate driving machine" of past BMW sloganeering, but has low CO2 rating. Not as covetable as a 5-Series once was.
Mercedes-Benz E220 CDi SE: £30,005, 170bhp, 139g/km
Latest E-class brings back Benz values of solidity and functionality. Next best to drive after Jaguar, too. Recommended.