7. 3 0PM, BBC F I RST The bad news? This feature-length episode constitutes the entire fourth “season”. The good news? That means there’s a lot of action in two hours. Our hero (Idris Elba, above) hunts a serial killer, gets a new partner, has a price put on his head, encounters a spooky woman and fights off thugs on a motorcycle with a rubbish bin. Phew!