Scenario
I asked a fellow dog-walker to prevent their dog from snapping at mine. They became very irate but I just walked away from the situation. I may have said "Please keep your dog under control in future" as a parting shot.
I presumed this was the end of it but months later this person spotted me, called the police and told them I had committed hate speech.
I was told by the police that they wouldn't arrest me straight away but I must come to the police station for interview the following day.
In fact the police called me the next day and said the complaint had been withdrawn and there was no evidence of wrong doing. They even apologised.
Question
This whole thing was completely unexpected but if I'd had the presence of mind to record the encounter on my mobile phone it would have proved I hadn't behaved badly.
Am I allowed to video such encounters under English Law?
Would such a video be admissible as evidence?