According to The Oxford School of Drama, Andrew Gower has been cast as a lead character. He will playing a vampire called Cutler, so I would assume that he is either Mitchell's 'replacement' or, more likely, will be of the Old Ones who we first saw towards the end of last series.
Since graduating last year Gower has appeared along side Lacey Turner (Lia from Series 3) in Frankenstein's Wedding 'Live in Leeds', and ITV's Monroe which starred James Nesbitt
Source: Oxford Drama School
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