You can make an allegation of dangerous driving and the Police will investigate it. However unless you have witnesses, preferably independent, or other corroborating evidence, such as filmed evidence, prosecution is unlikely to follow.
The pictures from a dashboard camera are not sufficient evidence to prosecute someone. They may back up other evidence though.
The police would not act on just evidence from a dashboard camera.
The police will also look at your driving. Easier to prosecute you if they can.
Saves them time and you produce the evidence. My advice is keep your dashcam records until they vindicate you.
I can see the frustration but I suspect insufficient resource to investigate every near miss someone brings them. Besides one can not tell if this is an indication of a dangerous driver of one miscalculation in a lifetimes of exemplary driving; so the value is questionable Investigating other crimes would have higher priority.
Not wishing to derail this, but dashboard cameras: do they remain on when the car is parked, so one can see evidence of deliberate vandalism or hit & run ?
It would depend on the severity of the drivers actions as has been mentioned.keep the footage because if there is another incident it would be beneficial to any outcome.
The 2 I have fitted, Front / Rear stay on after the car has been parked for approx 2mins, my opinion on dash cams, for the drivers protection, every car should have one, HGV's are now fitted with these due to claims from motorist's / Cyclists.