You can see the (original?) "Ken Dodd's Dad's Dog's Dead!" on White Hart Lane, near the stadium. It looks like it had been repainted. This is, to my knowledge, the only piece of "clever" 1970s graffiti that can actually be proved to exist. Nigel Rees used to get listeners to send in funny graffiti on some Radio 4 programme (Quote Unquote, etc.) in the 1970s and 80s, nearly all of which was obviously made up. By him.