Head and arm out of the window suggests he wasn't in proper control of the vehicle, which on the face of it - if there were witnesses and the will to prosecute - is presumably careless or even dangerous, just like driving with your hands behind your head ...
More provably, the Exif data on that pic should show what device it was taken on. I wonder if the Met's Cycle Task Force counts showing Clarkson he's an arse among its objectives.