Polari is a form of cant slang used in British subculture. Believed to have originated in the 16th Century, by the late 20th Century it was known to be used by homosexuals to discuss personal issues in general public without being understood. It is also known to be used both for normal conversation or for entertainment purposes by sailors, fairground showmen, criminals, prostitutes and Jewish people.
In Filthy, Rich & Catflap, the character of Ralph Filthy frequently uses Polari in conversation with various characters. It is never mentioned whether Ralph is a homosexual, so it is reasonable to assume that his connections with showbusiness are what has caused him to develop his manner of speaking.
The most well-known use of Polari in entertainment is in the puppet show Punch & Judy.