It's occurred to me that public entertainmnet isn't just music; a stand-up comic giving a performance would also be classed as entertainment.

So this would imply that anyone telling a joke in a pub - which by definition is open to the public and therefore "clearly public in that it takes place on premises which are open to the public" should also have a Public Entertainment Licence. And what about outside in the streets? You can't get more "open to the public" than that.