But he's so cute! I understand the sinister bit you're talking about when he went after his "wife" in season 2 when she came to the house and was taunting him. He's a big guy and I wouldn't pull his tail.
OT, but I must mention that he does seem to play a lot of the same type of characters in a lot of the movies he's been in (strictly incidental, me falling upon other movies he's been in, I promise! I ended up finding 2 other British drama's that have him in it) and he's supposedly this big burly guy people are afraid of, but he's a big softy, so maybe there isn't so much sinister if he remains true to form in character types.
ETA: He seems to play SOME of the same type of characters...apparently, he's in a lot more shows than I thought.