The Touring's lower stance helps too. The chassis differs slightly from the saloon; the rear suspension has been compressed to open up the load space inside the rear hatch as much as possible (the new model has 1650 litres of luggage capacity - 125 litres more than the previous version). BMW has also swapped the rear steel springs for air springs that automatically pump up to keep the body level when carrying heavy loads.

Boot space can also be increased by ticking the options box for the run-flat tyres. Although this will compromise ride quality, it does mean doing away with the spare wheel, thus creating a secret luggage compartment under the load floor.

The Touring also showcases BMW's new Head-Up Display, which is due for launch in the 5-series saloon and 6-Series coupe this September. It seems to work well. In its standard setting there's an orange digital speed display floating just above the bonnet line that becomes second nature to register, making the speedo redundant. Delve into the i-Drive menu and you can set it to display other information such as navigation and warning messages. Strangely, the display is invisible to the front seat passenger.

At the launch there were two models available, the 530d and 545i, both fitted with the optional six-speed automatic gearbox. Driving them back-to-back was fascinating. Up until now I've always thought that BMW's 3-litre diesel was a terrific engine. When it was first launched it seemed to redefine what a diesel engine could deliver to an enthusiast. Strange, then, that although the 530d powered down the autobahn with serious conviction, it frustrated on the twisting roads that formed the vast majority of the test route.

This 530d has the very latest version of the 3-litre straight-six engine. Power has increased from 193 to 218bhp, mainly by winding up the peak boost pressure of the single turbo. But in this form there's noticeable throttle lag. In combination with the new six-speed auto 'box, it means there's an annoying pause between ordering more power and it arriving at the rear wheels. Whenever we've tried the 3-litre turbo-diesel engine before, it's been in the 3-Series, where the lower kerb weight disguises the problem, but here in the 1760kg 5-series there's no escaping its baggy delivery. It's no wonder there's a twin-turbo diesel due in September; BMW must know that the single-turbo version has reached the end of the road in terms of output and delivery.

The driving experience in the 545i couldn't be more different, for here's an engine of peerless ability; strong at the bottom end, mighty at the top, and with the instant power delivery of the normally aspirated V8, it completely destroys the 530d for driveability.

The only fly in the ointment is price. The 545i Touring costs a whopping ΂£10,000 more than the 530d, so it's no wonder BMW predicts just 3per cent of Touring sales will be of the 545i, while the 530d will take almost half. Judged purely on ability, it should be the other way round.