There's no coupe equivalent because Audi says that the convertible is the big-seller in the UK, and it costs just ΂£21,450, making it a chunk cheaper than the 180bhp and 225bhp Roadsters (΂£26,300 and ΂£29,000 respectively), both of which have quattro four-wheel drive and six-speed gearboxes.

Effectively, the 150bhp TT has the underpinnings of the Golf GTI, with the lowest tune of VAG's ubiquitous turbocharged 20-valve in-line four, MacPherson strut front suspension and a torsion beam rear end. This simplification isn't carried through the rest of the specification, though. The 150 has all of those lovely aluminium cabin details that make the TT so appealing and all of the goodies of the more powerful models, including the neat electric roof, air conditioning, electrically powered glass wind- deflector and ESP stability and traction control.

Indeed, the only clue you'd have that you weren't in a 180 or 225 is the five-speed shift pattern on top of the gearknob. You're not missing out on any engine charisma, which is lacking in all 1.8Ts, and there are a couple of pleasant surprises in store once you get rolling. The first is that the shift of the five-speeder is slick, short-travelled and positive, a good thing to use - better than the six-speeder, in fact.

The second is that despite its horsepower deficit to the 180, the 150 seems to be almost as quick. Audi's figures suggest that there is less than a second difference between them to 62mph - 8.9 plays 8.2sec - and the 150 runs to a maximum of 133mph, just 4mph less than its bigger brother.

The reason it feels almost as quick is that at 1335kg it weighs a useful 130kg less, and with 155lb ft virtually matches the 180's torque/ton ratio. The engine delivers decent punch right through the rev range, peak torque arriving at 1750rpm and hanging around all the way up to 4600rpm. The gear ratios are well chosen, and dynamically it's a tidy enough car to hustle, with particularly well-judged steering weight (unusual for an Audi) and decent enough precision and feedback.

The car we tried was fitted with optional 17in wheels with 225/45 tyres but I'd guess that on the standard 16in rims, shod with 205/55s, the 150 would have similarly good dry road traction - the traction control intervenes lightly out of tight turns but switch it out and there's so little slip you wonder why it was activated. I reckon it would ride a lot better on the taller, narrower standard tyres, too; with the hood stowed, the 17s induce a bit more shake and shudder in the topless shell than you'd want, and more than I recall from the last Roadster I drove.

Against expectation, the TT Roadster 150 really is a bit of a bargain - you get the look, the equipment and a fair amount of the 180's pace for almost ΂£5000 less. Indeed, the entry-level Roadster is easily the least expensive way into a TT, being some ΂£2600 cheaper than the 180bhp Coupe. You don't get four-wheel drive, of course, but in the dry you won't notice that it's missing, while in the wet traction control and ESP will keep things safe.

So, a shrewd move on Audi's part, then? Yes, so long as it competes for sales with the lesser-engined BMW Z4s rather than just nicking them from the marginally faster 180bhp TT Roadster.