You should not get a prison sentence for “planning” something unless it’s terrorism or another act of extreme violence. I.e. the guy who was just jailed for planning to kidnap, rape, and murder Holly Willoughby.
Arresting people for planning a nonviolent protest is authoritarian behaviour.
This is the UK, land of the GCHQ (same as the NSA, but worse, and when the Snowden revelations brought up what they were doing, it was simply made legal, unlike in the US), the most video surveillance cameras per person in the World, were they’ve been using techniques such as kettling of demonstrations for years and were the police were early adopters of AI face recognition cameras.
That place is hugelly authoritarian, they’re just posh about it and their use of violence against normal people tends to hide behind “rules and regulations” unlike cruder nations were the cops just shoot them.