London slang sub culture isn't English anymore. The more u hang around and listen to chavs the more u become one urself.It's a bit more complicated. They might be originally Anglo-Saxons but most their words are Latin even with the Germanic grammar.
They're mutts made out of backward old Germanic tribes + Saxons and then Danish and Friesian invaders and later French rulers for the past millennia.
The most recent invaders are timojilec and geeljire so you can expect the English language to include some Urdu and geeljire soon.