BMW's latest X5 model, the 4.6is, is as close as you can get at present to an "M" version of the company's off-road competitor. And it may just stay that way given both the relative unsuitability of a four-wheel drive to wear the revered M badge, as well as the vehicle's obvious incompatibility with the M naming convention - X5 would need to become MX5, but that's not even a remote possibility given Mazda's hold over the nameplate for its long-running convertible sports car. With a reputation built on the experimental X5 Le Mans' sub eight-minute lap of the legendary Nurburgring race circuit, what's clear is the X5 4.6is is no ordinary four-wheel drive. Rather, for now at least, it is the ultimate expression of the recent crossover craze, where manufacturers continue to blur the lines between the once separate designs of car and 4WD.