In the largely homogeneous world of mid-priced family cars, it falls increasingly to Citroën - the company that has delighted us with such uncommon touches as the arm-wrenching, dash-mounted gear-shift, the sardine can-style sunroof mechanism and the self-inflating suspension - to carry the flag for eccentricity and downright weirdness.

It seemed to be keeping its end up not long ago with the release of a small MPV named, for no obvious reason, Picasso, which came with a pop-out shopping trolley, known hopelessly as a "Modubox", and with a sunroof so wide that there was almost nothing left of the bodywork when it was open. It's for unique and unpredictable developments such as these that one cherishes the marque.

Sadly, though, some abdication of responsibility seemed to have taken place earlier this year when Citroën launched the C5. Despite promisingly sharing a name with Sir Clive Sinclair's most famously still-born automotive invention, the C5 looked almost conventional and, worse still, was stuffed with boring old technical wizardry, rather than with the innovative plastic baskets on wheels one had come to expect and hope for.

I had imagined that the new estate version of the C5 would offer the same sense of disappointment, only with a bigger boot. In fact, I had imagined that the saloon's disappointing ordinariness would be intensified. Estate cars are, after all, legendarily the motoring equivalent of a deep and resigned sigh.

Nobody buys an estate car because they want to go fast, look flash and feel different from the pack. They buy an estate car because they want to go into the funeral business, or because they have children and all the paraphernalia that comes with them. Children make estate cars seem, if not attractive, then at least inevitable. To buy an estate car is to make the tacit admission that, for you, moving around has become a major task.

I took it all back, though, about the C5's disappointments when I used the estate version to go on holiday from London to Cornwall as a family of four. The car seemed to me, in those circumstances, to be little short of a miracle. It took everything four people could throw at it in the way of luggage and beach toys, with a smile and space to spare. It then drove with beautiful smoothness, as if plump with feathers, for four hours down a motorway and without needing to stop for fuel. (It was a diesel version.) Two weeks later, it would perform the same chore, with equal efficiency, with the same absurd amount of luggage, plus a fortnight's added rubbish and a tonne of Cornish sand, brought in off the soles of various shoes.

One soon stopped bemoaning the absence of oddities, and instead celebrated the car's wholesomely sensible features: such as the button inside the tailgate that lowers the tail-end to make loading easier; the opening tailgate window, which allows you access to the back without having to hoik up the back door; the reversible boot mat, which has a cloth side for dry goods, and a rubber side for animals and children; and the net which can be drawn up to separate the cabin from the hold and thus, during an emergency braking manoeuvre, prevents your passengers from getting it in the neck from a flying sand rake.

The sophisticated electronics that the estate shares with the saloon, seem to me, though fun, less obviously purposeful. The car adapts its suspension to suit the road surface, which is smart. But it can also mind the headlights and the windscreen wipers. Maybe I'm just uncommonly forbearing, but I have never really experienced the requirement to operate a car's wipers as an unreasonable burden. What's more, the C5's automatic system seemed to me to be rather panicked - shooting straight into rapid wipe mode at the first hint of rain. I kept wanting to tell it, "For God's sake, it's only a drizzle."

There is room to wonder if this push towards greater and more sophisticated automation isn't misguided. People tend to be fiercely protective of their reputations as drivers, and touchy about admitting to weakness or oversight. A car that makes up its mind how fast the wipers should go and when the headlights should come on is really just a quieter version of the nagging passenger. Worse, it seems to imply that it's a better driver than you, and an awful lot of road users who would be reluctant to take that information on board.

People will love the C5 Estate, I suspect, not for its automation, but for its space and speed. I grew even to believe that it was rather good-looking - though I wouldn't be the first to make that kind of mistake about a stranger encountered on a holiday.