Road Test: Audi A3 1.9 TDIe 3dr

Let's set aside the ethical debate surrounding the tax on motorists that has been imposed, not by the government, but by the mayor of our capital city. And let's briefly remove from our oft-troubled minds any fears regarding the environmental impact of CO2 emissions from cars.

Instead, permit us to focus on the real appeal of the Audi A3 1.9 TDIe - the potential it presents to wipe the smug, whining, Zippy-from-Rainbow smirk from Ken Livingstone's face.

Thanks to the combination of low-rolling resistance tyres, stretched gear ratios, low-drag bodywork and lower friction components used inside its 1.9-litre turbodiesel engine, this car slots in below the crucial 120g/km CO2 target that should, in theory, see its owners exempted from having to pay the C-Charge if long-talked-about regulation changes come into place.

The best part? This is no Audi-badged hair shirt. Inside, quality remains exceptional, as good as for any car of this price. If anything the taller gear ratios give a more relaxed gait away from the crush of central London, helping to reduce the rattle and chug of that diesel lump, while performance is perfectly acceptable day-to-day. And those fat-profile tyres and the absence of sports suspension make for a plusher ride than in any A3 that has come before.

The only concern is that the more cars like this that appear, the greater the risk that the 120g/km C-charge exclusion will be quietly ditched from the agenda. Ken, buddy, we're begging you here - don't do it.