You talk some crap sometimes. Amber light. Its an offence to drive through it. Read here https://www.gov.uk/guidance/the-highway-code/light-signals-controlling-traffic A cop is still a cop, on duty or off. He witnessed a criminal offence, and when back in uniform, pursued it. Dash cam is perfectly legal to use as evidence in ANY court proceedings or prosecution. Whether the judge allows it is a different matter. And finally, you state that he should lie, to a cop taking notes, on an official visit? Are you serious? Maybe the personal visit was just to make a point, and attitudes were not to his liking,

Let me see if I've got this straight in my own mind. You're advising the OP to (potentially) lie? So that if it goes to court and if the dashcam footage is admitted as evidence, the OP could possibly be convicted of perjury instead of a minor traffic light offence. That can't be right surely?