Perhaps the timing of the lights was messed up? But anyway. This is why I don't like this country: the roads are too small and too crowded, with too many people using it as an excuse to rage.
Actually no, the traffic was moving between 50 and 70 mph just after the Brynglas Tunnels on the M4... the BMW in lane 2 had been sitting on my rear quarter and had moved ahead as my lane slowed... the kid in the Corsa was totally oblivious to how close he was to causing a pile up... I was biding my time in a line of traffic in lane 3 waiting for it to clear...