This article on multi-ethnic London English (MLE) https://www.theguardian.com/education/2019/mar/29/ching-wap-ox-slang-interpreters-decipher-texts-for-court-evidence links to several courses I teach.
It shows how language and sub cultures interrelate and how groups might want to include and exclude certain kinds of people (there is a reference to "a “cryptolect” – a language meant to hide things". A link is made near the end of the article with Polari, which is studied in Exploring Languages and Cultures (L161).
The comment by a young "drill producer" that "If it was a young person like me translating it would be more accurate. You want to understand the context" could almost be the motto for understanding language and language use and context is certainly key.
It also seems that the variety is influential outside London and is even known in East Yorkshire so the language seems to be connected to a culture that transcends geographical boundaries.
It was also interesting to read the origin of words (mainly Caribbean but with some Arabic and Polish) and this presumably reflects some of the origins of some users.