Here is some more people arrested to prevent a breach of the peace.
Met police: 21 people arrested on King’s Coronation day to face no further action | Evening Standard
Did the police think the crowd would turn on them?
If the police think that a crowd could turn violent - then what should they do?
Should they protect the person from the crowd?
Should they arrest the people who they think might turn violent?
Should they suggest to the person who might be the target of the violence that they move?
Or should they do nothing and hope the breach of the peace does not happen?
And if it does, then clearly they haven't prevented it.
If someone is standing, wearing a t-shirt that might cause some to be violent towards them- what should happen?
If someone who is Jewish is by a crowd where it's clear that there are members of who could turn violent towards them, what should happen?
And if you have different answers to that, then why?