When I first met my cousin's from the UK, I thought they'd speak like the queen. To my surprise they spoke like they were raised in the gutter

I can't take them seriously.
It's the jamaican influence on the british accent for youth that's making them talk like that. The Caribbean influence is also happening in Toronto, Somalis are influencing Toronto slang too through music. Xabad, kawaal, walaahi, saqajaan etc.. are all making it mainstream.
It's interesting seeing ajanibs using somali words in their slang.
