the white van is in the left lane which is only for leaving at the next exit. the driver then indicates right and carries on around the roundabout, this is both illegal and dangerous, the car in the adjacent lane can either leave at the next exit or go right, but not indicating, so suggesting they are leaving at the next exit, as the Mazda get near the exit, the driver clearly indicates left, the white van driver has not looked or just decided to make his dangerous manouvre anyway. A typical example of poor driving on a roundabout. It would have been a nasty collision as cars typically travel at 30-40 mph at this point on the roundabout. It is Junction 21A of the M25 heading for St.Albans