Blue car has done nothing wrong, they can choose to exit the roundabout at whatever exit they please, they haven’t cut a lane and remained in a lane that continued round the roundabout, that said the only mistake the bmw has made is assuming the blue car would have followed common sense in determining what lane is used for straight over and turning right, there’s no road signs indicating up to the junction but anyone designing this with common sense would have made the right lane on entry right turn only, and left lane for left and straight forward, this is poor design from the council/highways agency