Line of Duty fans believe Chief Constable Philip Osborne is the most likely to be unveiled as 'H' in this Sunday's series finale, a poll has revealed. The BBC drama has gone from strength to strength since its release, growing from an initial audience of four million adults to more than 11 million tuning in for the current series' penultimate episode. The show sees the officers of police anti-corruption unit AC-12 pitted against the mysterious antagonist known only as 'H' or 'the fourth man', who heads up an organised crime syndicate controlling events from the shadows and potentially from within AC-12 itself.