I think the big bright bold type on the sash 'CLIMATE EMERGENCY' should be a clue what they there for even for the myopic and hard of thinking.Hardly. She entered a private function with The Chancellor in attendance. Like it or not, politicians are targets for assault and worse, as we saw with Jo Cox. She was a trespasser with an unknown motive who disregarded all attempts to verbally stop her. That is not just walking onto a room.
Only time I've seen someone receive a kicking at a major event from officialdom was in Sri Lanka in 2001 (still Tamil stuff going on then) at Dambulla during a cricket 1 dayer - Many locals flooded in without paying and sat in the stadium to watch. Then when armed police went to investigate one local made the error of trying to grab a gun. He was hauled out from the stand and a group of police laid into him on the outfield until they realised the televised match had stopped to watch - players umpires, tv cameras etc. - so the police grabbed his arms and legs and carried him round the back to finish off in privacy what they started...