Agree with you Aileen. Trafalgar Square used to be disgusting. One of the best things Ken did was employ a Falcon to sort them out...
I'm sure Wimbledon has a falcon as well. I wish Edinburgh would get one for the east end of Princes Street Gardens where the food kiosk, so plenty of crumbs - and I've even seen visitors feeding the darned pests!
I bet you wouldn't be amused either if it happened to you. Do you have any idea just how difficult this muck is to remove?