^
It needs clamping down on, ideally the plod could identify those responsible and fine them the full amount allowed under the law. We're too fucking soft in the UK with this kind of shit.
I agree we shouldn't just point the finger at students, as there will have been other non students. However, I would expect students, in whichever City they study in, to show respect to the place and tidy up after themselves. They wouldn't like it in their home town, so why is it acceptable in Liverpool, Leeds or Manchester? I reserve a special disdain for the locals, they live there, they should know better.