What? UK is like the poster child for arresting leftist people on no ground at all. Started in the 80s (it might have been even earlier). I mean, France isn't far behind, but at least we dissolve far right groups too (well, after they kill people, whereas no far left group has killed anyone yet).
I think the most recent was Toby Child (Correction, Toby Shone), but there was a Walker something arrested for owning "the Anarchist cookbook" in the last 10 years, and more recently multiple members of extinction Rebellion were arrested juuust before an authorized protest, on no ground, for no particular reason, which -what a surprise- prevented them to assist the protest (This is actually a French tactic, good job implementing it UK police).
It really picked in the 90s against "ecoterrorists", but arresting lefties is like 50% of your counterterrorist police job, because they smoke pot and like to trespass a lot, which give ground to search their home and arrest them for cannabis possession (or fuck with them, just because) and way less dangerous than going against real terrorists with guns and explosives.
What i find really weird is people complaining "It's always against my camp", forgetting that most of the time, it's actually not.