Car A and B are driving down a dual carriageway that has a section of 50mph speed limit and the rest is 70
Car A comes out of the 50 section in the left lane and picks up speed, coming up behind car C still going 50. The road is pretty empty bar car B which is in the right hand lane some distance behind - at least 20 + car lengths who has also just come out of the 50 zone and picking up speed
Car A sees car B in mirror but due to speed of car C either has to brake or overtake Car A pulls out and overtakes car C quickly going back into left lane but does not realise car B is going 90mph.
Car B is very angry and had to slam on brakes although car A does not stay in right hand lane for any longer than needed to overtake 1 car
Car B driver flashes lights beeps horn multiple times even once has passed car A, then makes offensive gestures pulling level with car A then at the next roundabout opens window and shouts at car A driver for being a stupid ***
Clearly car B did not react very well but was this proportionate to what car A did, a normal driving manoeuvre making the assumption that car B was going around 70mph and therefore had plenty of time?