Richard M Hammond drives the Vauxhall Astra that is 'ecoflexing' its green muscles.

In its decades-old battle with the Ford Focus and previously the Ford Escort, Vauxhall's Astra has often come out on top as the UK's best selling car.

The battle has been played out across a number of scenarios from the Astra GTE versus Escort XR3i conflict of the late 1980s to the soft tops of the mid-Nineties, but in these more austere times the contest is to be the most frugal.

The non-stop-start version is cheaper to buy but loses out, albeit marginally, in terms of fuel economy and emissions. With the Astra, this is not really an issue with the Vauxhall dropping from 109g/km to 104g/km so remaining in tax band B and comparable with the new Focus.

Compared to the Focus, the biggest thorn in Ford's side comes in the form of the new Astra's interior.

The Focus's upmarket, high-quality interior has been a large part of its 'class-leading' appeal, but the current generation of Astra has upped its game in this regard.

There's a high-quality ambience in the cabin, giving the Astra a mini-Insignia feel. Material quality is very good and plastics are soft to the touch but sturdy. In the Exclusiv model, soft lighting beneath the gear lever surround and in the door handle moulds is a premium touch and the chunky, sturdy feel to the steering wheel is replicated around the interior, in the metal-rimmed knobs and the solid column stalks.

The Astra holds its own against its closest rival from the outside, too. Like the Focus the Astra boasts a contemporary design that's attractive but refined and sensible.

The ecoflex model needn't suffer visually for its greener emphasis, either – 17in alloy wheels are optional to replace the flush-covered steels as standard. The revised aero package does little to harm the Astra's attractive exterior lines and the automatic aero-flap behind the grille is discreetly hidden. A particularly keen eye may even spot the marginally lowered suspension, which reduces drag alongside the low-rolling resistance tyres.

However, the major changes, although still hidden from view, are more noticeable. The taller gearing, for example, which comes courtesy of a longer final drive ratio, affecting all five-forward gears. The positive side is that high-speed and long-distance cruises are more refined thanks to lower revs. This works well with the Astra's impressive ride quality, even on the revised suspension.

It does result in less inspiring straight-line performance than some eco rivals, however. Using a smaller capacity diesel engine seems like an obvious way to reduce fuel consumption and works very well around town, but when greater acceleration is needed the 1.3-litre unit does need to be pushed harder and kept above 2,500rpm for any real performance. This means the engine remains audible in the cabin, too, particularly when cold.

A lower idling speed counters this slightly in the standard ecoflex model, but not as much as the zero-idling philosophy of the stop-start equipped model.

On the move, the Astra can hold its head high. Ride quality is very good and the chassis is responsive but predictable and secure. Electronic stability control is standard.

An accommodating interior boosts the family appeal. Boot space behind the hatch is conveniently proportioned with a bigger opening than initially appears from the outside. The rear bench will accept two adults with little fuss, too, with good access.

The stylish and noticeably well-built Astra is impressive enough to keep the contest with the Focus alive for the foreseeable future.

VAUXHALL ASTRA 1.3CDTI ecoFLEX EXCLUSIV

Price: �18,385 on the road (with stop-start �18,730)

Engine: 1.3-litre, 95bhp turbo diesel

Transmission: Five-speed manual driving the front wheels

Performance: 0-62mph, 13.8 seconds; top speed 109mph

CO2 emissions: 138g/km

Economy: 68.9mpg