You may have seen a recent Catherine Tate sketch in which some privately educated upper-middle little darlings take part in an egg and spoon race.

One mother discovers a carton labelled “economy eggs”. Mortified, she bellows “they’re not organic” down the track, whereupon the entire field scream, drop their spoons and flee towards a fleet of identical silver BMW X5s.

BMW must have loved it. It knows that a typical X5 owner is not above a gentle ribbing and that the brand benefits from the X5 being seen as a non-negotiable component of a lifestyle aspired to by many.

But in the real world the X5 has never been that great a family wagon and has sold largely on image and driving ability.

Despite its size it didn’t make good use of space, with not much room in the back and a boot even smaller than the one in the X3, its cheaper sibling. It handled well but rode like a tractor with flat tyres.

This all-new X5 is here to change that. Available next April from £40,085 with a 3 litre diesel engine or £49,945 with a 4.8 litre petrol motor, it has grown in every direction so that there’s now not only more than enough legroom for five adults, for the first time (and for another £1,000) there is the option of a third row of seats in the boot area.

Unlike in the Audi Q7 or Land Rover Discovery 3, these seats are not designed to take adults, but for pre-teen children on a school run they are more than adequate.

BMW has also been hard at work on the other rough edges. A new suspension philosophy has resulted in ride quality as good as its predecessor’s was lousy, while its interior has a feeling of quality the old car never approached.

So when you climb aboard and set off it appears transformed for the better. I’ve only driven the diesel but its performance is such that I’d question the wisdom of anyone wanting to spend nearly 10 grand more on the very thirsty petrol version. It responds well to commands from your foot, squirting effectively past traffic yet cruising at high speed in near total silence.

It’s no rocket ship but by its class standards the performance is more than adequate. Only the gearbox, with its lumpy shift quality in sport mode, is a tad disappointing.

And when you come to some corners, most will think BMW has done that most difficult of things: improving ride quality without a commensurate deterioration in handling.

It swings from curve to curve with an authority that’s rare in an SUV weighing more than two tons, and only that tiny proportion of owners who drive it really hard will ever discover that the fine edge of handling excellence, the agility and balance that so distinguished the old X5, has been sacrificed.

Perhaps that shouldn’t matter, but to me it does. Ever since the X5 invented the sporting off-roader back in 1999, the fact that it was genuinely fun to drive set it apart from the pack. Even when Porsche and Land Rover tried to muscle in with the Cayenne and Range Rover Sport, the X5 remained the pick of the three.

But now the very thing that defined the X5, gave it its character, built the image and helped ensure that a staggering 580,000 of them emerged from BMW’s plant in Spartanburg, South Carolina, in just seven years has gone.

Am I being picky? Probably, but it is the natural way of things for cars to become more boring to drive with each successive generation, and one of the things I have admired most about BMW over the years is its determination to buck this trend. Not this time.

Still, there is a bigger issue here. Though the X5 may now be just another car in the growing ranks of two-ton SUVs, I’d be surprised to find out it was not the most accomplished. It is better looking and more spacious than a Cayenne, quicker by far than a diesel Range Rover Sport, almost certainly more comfortable and rewarding than an Audi Q7, and its option of a third row of seats gives it something you’ll not find in a VW Touareg or even the hitherto class-leading Mercedes-Benz M-class.

But I’d advise you not to buy one yet. However good this diesel engine is, there’s a much better one coming in about a year’s time with a power output up from 232bhp to 286bhp, apparently without any serious impact on economy or emissions.

If BMW takes the opportunity to firm up the car just a little to handle the extra performance, the result could just be the finest SUV of them all.

VITAL STATISTICS

Model BMW X5 3.0d SE
Engine type 2993cc, six cylinders
Power/Torque 232bhp at 4000rpm / 383 lb ft at 2000rpm
Transmission Six-speed automatic
Fuel/CO2 32.5mpg (combined cycle) / 231g/km
Performance 0-62mph: 8.3sec / Top speed: 134mph
Price £40,085
Verdict Improved in most areas, but less fun to drive
Rating Four stars
Date of release Next April

THE OPPOSITION

Model: Audi Q7 3.0 TDI £37,330
For: Spacious, good-looking and effective interior, image
Against: Heavier, thirstier and slower than X5, ride quality

Model: Mercedes ML 320 CDI £37,220
For: Looks, can be used off road, frugal and powerful
Against: Available only with five seats, a little dull to drive