Mind the paraphrasing, but from what my friends who were at the protests said, there was no warning given before gas canisters were thrown. The warning came is dispersal. Were there armed leftist groups at the protest? Of course, they happily idetified themselves as such. Despite this, no arrests were made and no suspects listed for assaulting a police officer. The more likely scenario in my head was police officers, who were deployed in sweaty, itchy riot gear got a little impatient and wanted to wrap things up faster than spend more time in the sweltering weather.
Mind you, I cannot be sure, but the fact that our local newspapers who all lean to the right are refraining from throwing stones (get it?) at the protestors and mentioned an internal investigation gives me pause.
Also, not sure who mentioned it and I couldn't be bothered to quote them, but Churchill deliberately ignored a famine in India during WW2 and even lied to the allies about the U.K. grain supply because he was a racist asshole.