Themes. This issue of evo has a bit of an oil-burning slant, and I don't mean worn valve guides and shot piston rings. There's a strong body of evidence to suggest that diesels will account for an ever-heftier slice of car sales, and that includes performance cars. Today's best turbodiesels can match a same-size petrol engine for power and far out-muscle it for torque, while using less fuel and delivering a relaxed, but no less rapid, drive. Some of them even sound bearable, if hardly the aural stimulator of track-land fantasy.

Martin Leach, under whose control lies the future feel of European Fords, is convinced that the performance diesel is the way ahead. A good thrash in a high-revving petrol car can turn hostile heads, but a diesel flashes past without advertising its pace. That said, past diesel-fuelled Fords have hardly been machines to covet, so it might seem strange for a Ford man to hold such a provocative view.

Bring on, to make or break Leach's case, the Focus TDCi. The Focus part is fine; the world is pretty much agreed that no other current lower-medium hatchback is as crisply entertaining to drive as this one, thanks to precise, slack-free steering, great body control and an interactive balance. The TDCi part - well, I'll explain.

When Ford launched the current Mondeo, one engine option was a new Duratorq 2-litre direct-injection diesel notable for lacking the diesel must-have of that moment, common-rail injection. It was on its way, we were told, including a 1.8-litre version for the Focus.

Now they are here, leaping from the gutter of dieseldom to the crown of the road in one leap. This engine uses a 'second generation' common-rail system, whose small pre-squirts of fuel before the main dose give a gentler increase in combustion pressure and thus make it sound less percussively dieselish. Other on-the-pace ingredients include a variable-nozzle turbocharger and an intercooler.

In Focus form, this engine produces 115bhp (acceptable for 1753cc) and 184lb ft of torque (pretty good). That peak power arrives at just 3800rpm, torque crests at 1850rpm, and if you're accelerating hard there's an overboost mode which releases another 22lb ft to make 206. Now we're torquing.

Those peaks occur at speeds laughably low in petrol terms, and enable the Focus to run stupendously long gearing - almost 30mph per 1000rpm in fifth. Economy benefits, as do CO2 emissions which place the Ford in the cheapest tax band. Which is fine, as long as it's a tolerable drive.

Prepare to be surprised, then. This state of mind arises as soon as you start the engine. It ticks away quietly to itself, no loose-nuts-in-the-cylinders clatter, no sub-woofing vibration. This is impressive for any diesel, never mind a Ford one, and seriously shades the much-vaunted VW and PSA turbodiesels. Now we move off, and... I've stalled it. That's pretty unusual for a diesel, too. Blame the long gearing.

Now we're under way. The engine feels crisp, the gearchange is precise, well-oiled and slop-free, the sound is recognisably diesel but distant. And there's a great torrent of torque on tap just as soon as the turbo spools up to speed, which happens quickly, progressively but urgently if you let enough air through the engine to trigger the overboost.

You have to stay in third gear in a 30mph zone because the gearing makes the engine grumble in a higher ratio, but out on an open road the cruising is so relaxed as to render your licence deeply vulnerable. You just can't believe there's so much pace for so little fuss.

Hills are a real blast. You can steam past trucks with no more than a pedal-squeeze, and the way the Focus squirts from legal to penalty points in fifth gear is just extraordinary. This car would surely cover the ground as quickly as a Focus ST170 on real roads, surfing on a wave of torque as the ST revs its gasflowed head off.

And, like I said, this isn't even meant to be a sporting car. Try one. You have nothing to lose but your prejudices.