I frequent more London hospitals than I would like, not by choice of course and mostly on the outskirts, despite not seeing any overt gang action whilst there the A&E is not a nice place to be at night. (counted I've been to 11 in the last decade mostly whilst caring for others) There are also homeless people living in the underground car park and asking for food in the canteen in the main one I go to. I have also seen the security in action a number of times for angry 'patients' who expect everything done for them instantly.
As an aside the hospitals in Central London are top quality with some of the best surgeons and specialist staff in the country, the ones on the outskirts less so but anywhere with an A&E is looks like a war zone. Actually went to an A&E in a more rural setting away from London year ago and couldn't believe how civilized it was.
Most of the people who work in all these places are heroes and don't deserve the violence and disrespect they get off these idiots