If Dr Who wished to demonstrate his sense of humour, he would drive the new Audi A5. Unlike the good Doctor’s Tardis (Time and Relative Dimensions in Space), the interior of which is the perfect example of the estate agent’s dream of “deceptively large”, the Audi’s living space is a mite cosy.

The label says that it is a “four-seat coupé”. Does that mean six-footers can sit comfortably in the back seats behind equally tall adults in the front, or do tall blokes sit in the front and smaller females have to struggle into the rear seats? That sounds like big trouble.

Although the A5 will carry four people of unspecified stature, it should be classified as a generous 2+2. Nothing whatever wrong with that — lots of coupés are — but I do like to know what I am getting myself into and, as a six-footer, getting into the back seat was a struggle, getting out even more so. While I was in there, my head was against the ceiling and, as for kneeroom, there was rather more knee than room.

All slightly weird because this handsome piece of quality German engineering looks large enough to carry four adults in comfort: based on the chassis elements of the next generation A4, it has an elegantly lengthy wheelbase of a shade more than 9ft and an overall length of 15ft 2in.

It feels big to drive, too. Not clumsily so, but it is more of a grand tourer than the sports coupé that Audi claims it to be.

Audi’s efforts to enhance its handling by stretching the wheelbase to 9ft and getting the front suspension as far forward as possible pay dividends, with reduced understeer and a feeling of balance. Sophisticated trapezoidal rear suspension helps, too, and with quattro all-wheel-drive (60 per cent rear-wheel torque bias) the car can be hustled along quickly and very safely, particularly in S5 V8 form, stitching corners together to create a smooth tapestry of tarmac but without quite the honed sharpness that I had expected.

The S5’s 4.2litre 349bhp engine does the sound business, though, emitting a powerful rumble to warm the cockles of your heart. CO2 emissions are 298g/km and combined fuel consumption is 22.7mpg (15.8mpg for urban), but the performance figures include a 0-62mph time of 5.1sec. Hang about it does not.

Rather more planet-friendly, but still very quick, is the V6 237bhp A5 3.0 TDI quattro. It gets to 62mph in a mere 5.9sec, has a top speed of 155mph but a stingily impressive fuel consumption of 39.2mpg and CO2 emissions of 191g/km — the lowest in its class. Maximum torque of 500 Nm comes in at a only 1,500rpm and muscles through to 3,000rpm, eclipsing the S5’s 440 Nm. Another set of amazing Audi diesel figures.

The S5 (£39,825) and A5 3.0 TDI (£33,430) are the launch versions of the new coupé. Coming later will be other petrol engines and a 2.7litre diesel that is likely to be a favourite, with 42mpg fuel consumption and 0-62mph time of 7.6 sec. A5 prices are likely to start from about £26,000 for a 1.8litre turbo-petrol.

The 3.0 TDI and S5 that I tried had six-speed manual gearboxes that had an obstructive action — hardly the norm for Audi’s fastidious attention to quality. The company said that they were not typical and the problem would be sorted out. I hope so, although almost half of buyers will sensibly specify a six-speed auto gear-box, or, on some versions, a multitronic CVT that is effectively an eight-speeder.

In the past five years, Audi has demonstrated its ability in several respects to equal or surpass its arch rivals, BMW and Mercedes-Benz. It has gone from ten models to 25 in ten years and the company talks of “fabulous sales progress” in 2007, with many more good things to come.

That level of growth is fine, provided that the focus remains on quality, design, enhanced dynamics, the ability to maintain the projection of individualism that Audi has traditionally managed — and that each model is precisely what the label says it is.

Specification
Car Audi A5 3.0 TDI quattro
Engine 3.0litre V6 turbo-diesel 237bhp
Transmission Six-speed manual
Performance 0-62 mph 5.9sec, top speed 155mph
Fuel consumption 39.2mpg combined
CO2 emissions 191g/km
Price £33,430
On sale July 14
Alternatives: BMW 3 Series Coupé Highly competent, great engines, so-so rear styling
Mercedes-Benz CLK Practical, showing its age, not very sporty
Volvo C70 Steady, safety-conscious drive