Kenneth Williams was one of the greats in a long line of British comedians who play extremely camp comedic characters. Julian and Sandy were known for being two camp homosexual characters in mass entertainment at a time when homosexuality was still illegal in the UK, and for their use of Polari in their sketches.
Polari is a gay slang language that was used as a code language when homosexuality was still illegal in the UK - it enabled people to talk about gay subjects without being understood by others such as undercover police. Although Polari isn't often heard on the gay scene anymore, some of the words have filtered down into everyday usage. Most people have no idea where the word 'naff' comes from or what it really means.