The new Astra is developed from the old car but is completely revised. It's longer and wider and the cabin is much more modern, with a coherent, wedgy, character. And under the skin? The new Golf and Focus have sophisticated independent rear suspension; costly and bulky, but effective. The Astra doesn't.

Engineers say that the marketing team had demanded 'better dynamics and less understeer, but nobody asked for four-link suspension - 95 per cent of people don't care what axle the car has'. They were a little defensive on this, but I felt for them. It's this kind of detail that some in the press can - cluelessly - latch onto and flog to death.

Instead, the Astra has a development of the familiar torsion beam rear axle. Normally this is simply a steel tube with trailing arms welded onto each end, but the new design has the tube punched into a U-section. This beam comes in two wall thicknesses and the trailing arms are welded to it at different angles to suit the engine size and chassis type (standard or sport). It also acts as an anti-roll bar. Meanwhile the new hollow cast trailing arms are stiffer and lighter.

It's a neat solution: cheap yet adaptable. Aside from improving agility, Vauxhall says the axle is tough, easy to manufacture consistently, frees up enough space for an extra fuel tank (for dual-fuel cars) and allows a third row of seats on the Zafira MPV model. At the front, the Astra has a big, stiff, hydro-formed subframe onto which is mounted the suspension and speed-dependent electro-hydraulic power steering. There are two rack ratios: sport and standard.

The Astra's real USP is its electronic chassis systems, based around 'ESP Plus' and sophisticated ABS. Even fairly basic models have Understeer Control, tyre pressure monitoring and deflation detection, a towing stability program and even Hill Start Assist.

At the top of the tree is the 'IDS Plus' (Interactive Driving System) suspension set-up. This includes CDC (Continuous Damper Control), which uses sensors - two for wheel acceleration, three for body acceleration and a steering angle sensor - to adjust the damping rates on all four corners in milliseconds. CDC can also 'talk' to the car's other electronic systems. There's the option of a BMW-like 'Sport' switch, too, which sharpens up the steering, throttle and CDC responses as well the shift pattern for the auto 'box. IDS Plus, including CDC, will be an ΂£800 option on other Astras.

These Astras are among the first Vauxhalls to feature switchable ESP (largely because the press was unhappy at being unable to disable the system), but when the ESP is off, ABS activation automatically re-engages it.

On a circuit so slippy it was hard to stand up, we were told not to correct oversteering tailslides but to wait for a split second - the response of an ordinary driver. The IDS Plus/CDC kicked in, sometimes just activating a single rear brake calliper, and, amazingly, the tail would pop right back into line. In some circumstances the system was subtle enough to feel like rear-steering, so effective was its marshalling of the rear end. We need to try it on tarmac, but I was impressed by its potential.

Despite the unusual conditions, it was possible to get a good flavour of the 200bhp Astra Turbo. It felt light on its feet and had excellent steering feel - very linear, if a touch over-assisted. The engine was very relaxed but punchy, and the six-speed shift was smooth and short-throw - a huge improvement on the old model's. The multi-adjusting seating position was excellent, and the suspension did a fine job of isolating the cabin from rough surfaces.

Complaints? The Astra feels smaller than the Focus and is, on first meeting, a little self-effacing. But I liked the car's obvious honing, subtle competence and attention to engineering detail. We'll know more in a couple of months. In the UK we'll only get a 175bhp version to start with, though a full-monty 240bhp engine (based on the VX220 unit) will be offered later in the funky three-door body.