On the M4 in South Wales last night, wafting along in the mighty Panzer at 75 mph in lane 1, engine emitting a gentle rumble at about 1,700 rpm. I could feel the power under my foot, just waiting to be unleashed but I was enjoying the run and my rowdy music. Ot was dark, drizzling and misty. A car goes barrel-arseing past me in lane 3 at about 95 mph. What was it?