"Even if Banksy did turn up, no-one would know it was him."
True. So maybe there could be an "I AM BANKSY" PLINTH PARTY, inviting anyone and everyone to come along and impersonate him. Obviously it would be an open invitation so that anyone could turn up and pretend to be him - even 5'2" career advisers. Yep, admit it Rosemary, you're probably a dab hand with a stencil. I bet you'd love to have Banksy as an alter-ego! Maybe it could be Banksys en mass (or is it Banksies? Or Banksii? OK, what is the plural of Banksy?) Or maybe, with a little forethought and preparation, there could be one Banksy at a time... a different Banksy for every hour, 24 hours a day, for, say, a hundred days....oh no, wait a minute........ 
Meanwhile, in London this Saturday.... http://www.progressivelondon.org.uk/conference/progressive-london-conference-2010.html