‘What we really need is a faux-historical drama series about police brutality and black activism set in 1970s London,’ said no TV viewer, ever. But TV commissioning editors have more important priorities, these days, than mere plausibility, entertainment or value-for-subscription fee. So naturally, when the chance arose to make Guerrilla (Sky Atlantic, Thursday) — a six-parter about Black Panther-style revolutionaries, starring Idris Elba and written by the guy who did 12 Years a Slave — the senior luvvies at Sky were on it like a mistimed high-five.