Apparently criminals have rights too and can sue you ,the property owner ,should they injure themselves whilst climbing the wall. Unbelieveable! However, should you catch them then you can use 'reasonable force' to protect yourself or your property, but don't chase them off the premises and then use 'reasonable force' as they run away as that is deemed assault or worse.
CCTV as said before in a public place, must have signs up to notify people of its presence, I suppose it also warns the criminals to keep their hoodies up and cover their faces.