Logic has left the building. Or at least it will do when someone walks into their dealer and places an order for the new X5 4.8iS. Nobody needs this pumped-up caricature of an already brilliant 4x4. It’s a study in pointless extravagance and, at £58,025, costs £20k more than the pick of the range, the 3.0d Sport.

Even if you are hell-bent on a V8, you’d struggle hard to convince us that the 4.4 Sport and the resulting five-figure sum you’d have in your back pocket from choosing it over the iS wasn’t all you’d ever need. The 4.6iS sold in tiny numbers, and the 4.8iS is likely to sell in similar amounts. So what is it about this car that’s so appealing?

Posture. The 4.8iS works brilliantly, like the 4.6iS before it. They hunker down on gigantic rims and exhale through funnel-sized exhaust pipes; tweaked X5s with enough bad attitude to send Mr T scurrying back to his GMC van with his gold chains between his legs. It’s an American influence: no longer is it enough to have a great car. To gain respect on the street, lilies need gilding, so BMW has reached for the gold-plate machine.

Doubtless the Germans could come up with some figures proving that the iS’s various body addenda, including the comical rear diffuser, add crucial stability to the X5 at autobahn speeds, but the effect on the high street is less certain. The 20-inch wheels are so wide the thing appears to roll along on four beer barrels.