Black one near dartford crossing on m25

[Trappy]

I was sitting at the lights in my birds escort and heard a loud roaring from behind. It was in the tunnel so sounded EXTREMELY loud. Suddenly this black fd (k-reg) shoots past going pretty quick and went straight on (don\'t know the road) with a black porsche boxter right behind. I tried to go slow as i went round the roundabout to see the inevitable outcome and just saw it edging away from the \'german car\'. I think it had red rims? Anyone on here? How did you do?