This is a classic setup. They have been asked to leave for "elf and safety" reasons. And who can argue with that politically correct concept? The protest must stop to comply with "elf and safety".
If that doesn't convince them to pack up and go home, the next thing that will be tried is the good old "carbon footprint" trick. They will be told that being gathered together in such large numbers, produces too much carbon, and they should pack up and leave immediately.
If some of them have their doubts about the veracity of the "carbon" claims, the Guardian will probably run a week's worth of stories about the "carbon" danger, together with pictures of men in strange suits and helmets carrying carbonometers and declaring that this is hastening the end of the planet.
Meanwhile the bankers will carry on as per usual, bagging their bonuses and laughing all the way to the bank.