What is it?
The diesel version of Audi's new entry into the supermini segment, offering the combination of decent performance from a 103bhp version of the company's 1.6-litre TDI engine plus serious economy 70.6mpg on the official combined cycle.
The A1 TDI's CO2 emissions of 105g/km are impressive enough, but they put it just outside the sub-100g/km bracket which delivers free road tax. Curiously, Audi will offer European buyers a lower-powered version of the same engine, which combines 89bhp and 99g/km, but it won't be coming to the UK, for now at least.
The official explanation is that diesel is reckoned to be a minority choice among British A1 buyers, with two-thirds anticipated to opt for either the 1.2 or 1.4 TFSI petrol versions, and so the marginal savings mean it's not worth offering the car with two different TDI engines.
What's it like?
Unsurprisingly, the A1 TDI's on-road appeal is broadly similar to that delivered by the petrol versions. There's no doubting the baby Audi's sophistication, and the well-finished cabin is a couple of steps beyond anything else in the segment in terms of the level of quality you perceive from the driver's seat.
However, first impressions also suggest that Audi's anticipation that the majority of A1s will be chosen with petrol powertrains is justified. The diesel is a willing enough performer, but it doesn't suit the car nearly as well as either of the refined petrol motors.
Its relative loudness is emphasized by just how well-insulated the rest of the A1 is and, as in its other installations, the 1.6 TDI suffers from a narrow powerband and needs to be revved forcefully to make more rapid progress.
Once cruising speeds are reached the engine note fades and the TDI proves itself a relaxed, long-legged powerplant, capable of pulling the tall gearing of the standard five-speed manual transmission without complaint DSG isn't available with the diesel motor.
Should I buy one?
There's lots to like about the A1 TDI. Like it's petrol-powered siblings it offers a new, cheaper way to gain membership of the Audi club and it will also be covered by the same £250 five-year/ 50,000 mile servicing offer.
It's also worth mentioning that, despite the A1's Polo-based underpinnings, the TDI is both cleaner, quicker and, most impressively, cheaper than Audi's last small diesel - the considerably more radical A2 TDI - was when it was launched back in 2001.
But the A1's petrol engines are so sweet, and so economical, that we suspect only drivers contemplating using an A1 for the sort of mega mileages slightly out of keeping with its supermini character will opt for the TDI motor.