The BMW X5 is just three years old, still has a waiting list of buyers in many of its most important markets, and on the face of it there was no reason to muck around with such a successful car so soon.

But BMW don't stop innovating just because everything is currently rosy. And at a time when normally there might be a bit of mid-life cosmeticising they've given the luxury end SUV that they regard as a benchmark in the class a pretty major upgrade under the floor.

Most of it is the installation of their unique xDrive intelligent 4WD system, which saw its first muck in the X3 that still hasn't got to Ireland. But there has also been an upgrading of engines and the addition of a new one at the top of the line.

The performance tweaks are most noticable in the 3-litre car, which, thanks to the new engine that we recently also drove in the new 5-sries, has had a substantial increase in power from 184bhp to 218bhp, and pulls almost a quarter more torque at 500 Nm. The bare-bones result on the road is an acceleration that has improved the 0-100 km/h from 10.1 secs to 8.3 secs.

The improvements in the 3-litre petrol version are limited to a 0.2 second inprovement in acceleration, but the 4.4-litre V8 car is a full half a second faster to 7 secs for the sprint and there's been a 34bhp boost in power output with the new engine.

The real new news enginewise is the 4.8-litre V8 which has a whopping 360bhp burbling under the bonnet and enough torque to pull another of its kind along behind and not even notice. The sprint here is a Porsche-like 6 seconds ... and this is a pretty massive SUV.

However, it is the xDrive that is the story to be told. In essentials, it is operated using an electrically activated multiple-plate clutch that changes the drive distribution from axle to axle, in conjunction with the familiar dynamic stability control traction management system.

In road driving terms, this means that instead of relying on power-reduction from the DSC to keep an overcooked vehicle from leaving the road on a bend, the system shifts the power ratio between the axles just about instantaneously to give optimum control at any given vehicle angle and speed. It can intelligently deal with both oversteer and understeer situations, and change the axle power ratios in a continuum as everything changes.

This is all made possible by monitoring an enormous range of data, including individual wheel speed, steering angle, lateral acceleration and yaw rates. The ability of the eDrive to respond ten times faster than normal automatic AWD systems is its uniqueness, and the systems developed are proprietory to BMW.

The new X5 also gets Trailer Stability Control which automatically compensates for the dynamics set up if a towed trailer begins to 'pendulum'. It is a world first also.

Offroad, the Hill Descent Control that is standard on the new vehicle works using the electronics in the DSC instead of the car requiring a set of low ratios. We took one of the cars through the kind of rough woodland that no owner is ever likely to try with their X5 and found it to be right up there with some of the best 'full' offroaders.

We also drove the diesel version across the country in some of the most miserable conditions and on some pretty grotty back roads in Galway and found that the new X5 is a car in which you can feel very confident and safe, regardless of the conditions.

There'll be a more comprehensive review in due course. But we're now very aware of why the X5 is not alone still generating waiting lists, but that quite a few of those first-generation owners are already putting down their names for a new one.

Price range is €72,200-€101,600.