It's all well and good building estate cars, but there seems little point in doing so if you only make the boot big enough to swallow half an Ikea flatpack and just the wheels from your Bugaboo. The 'compact executive market' (Audi A4, BMW 3-Series and Mercedes C-Class) has always disappointed in this area.

What made this more frustrating was the knowledge that the estate versions were always the cooler models to go for. Especially in the Q-car spec, de-badged and with no frilly wings or wheels. I've lost count of the number of friends who got one of these 'estates' when the first kid came along, then had to swap it for something bigger when kid number two popped out.

That's been the main problem; designers have neglected whatever is their equivalent of the Hippocratic oath, and have been indulging in stylistic flourishes at the expense of functionality, apparently forgetting that there's a reason it's this shape in the first place.

It seems that if you want a big boot with your estate, you have to order a Vauxhall Vectra, where the squared-off rear gives you ample load volume but the dominance of functionality results in a car veering towards 'hearse spec'. It's not sexy, and it's not premium.

The new A4 Avant is claiming to change all this though. It's still not got a squared-off back end, but even so, boot volume is up quite considerably. It needed to be - the last version of the A4 Avant was pretty poor when it came to luggage space.

But this car has righted that wrong, as the litreage is boosted from 442 to 490 with the seats in place - seats down, you now get 1,430 litres, which is much more like it.

Audi claims this is best in class, but the differences are so minor (the C-Class has 485) that the result is negligible. It keeps Audi's headline-making department happy, but in reality you can squeeze just as much in the rivals.

All this extra space shouldn't come as much of a shock though. The new Avant is longer than the old car (28cm), wider than the old car (5cm) and has more length in the wheelbase than the old car (16cm), so to have failed to create more room would have involved a car where the sloping rear starts at the wing-mirrors. A feat of complete idiocy, in other words.

However, Audi has added some clever touches in the boot for this revamp which makes the space much more flexible. You can get an electric boot door as an option - useful for when your arms are full of the 2.4 children, but a bit too slow when you need to get in there in a hurry.

The neat boot dividers that you can get as an option in the A6 Avant are carried down to the A4 - a luggage net and tie-down eyes are standard, but the sliding dividers are much smarter and neater.

In typical Audi fashion, they clunk into place in a reassuringly expensive manner. And a reversible mat is also standard, which is a simple but smart idea. Country types buy these cars, and country types get muddy wellies and dogs from time to time.

It's not all good news though. The luggage cover now slides up along rails on the inside of the D-pillar, as well as retracting back freely towards the rear seats. That's a good idea in principle, because it means you don't have to faff around pulling it backwards and forwards every time you put some luggage in - it simply slides up the rails. But the execution isn't quite what you expect...

Audi's famed build quality seems to have taken a long lunch when they were putting this together, because the luggage cover isn't damped. Besides, a similar system in the BMW5-Series automatically slides back down the D-pillar when you close the boot.