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the protesters will fuck off back to London and console themselves that if they hit targets in the capital they might get more publicity
Heavy-handed police responses are usually counterproductive in these situations - photos of protestors being dragged away in handcuffs are pretty powerful. Whilst the experience in the cells will have been thoroughly unpleasant for the LBC journo it also gives her a massive platform.
I think the truth is that the Herts chief constable wants to shunt future protests to some other force. They're a huge drain on police resources, especially for a smaller force. If he goes over the top and puts press and/or protesters in the cells overnight and searches their homes, the protesters will fuck off back to London and console themselves that if they hit targets in the capital they might get more publicity.