ITV1 really, really loves that succulent two-hour slot in the middle of Sunday evening, and anything that goes in there has the legacy of Morse, Lewis, Frost, Miss Marple et al to live up to. The latest cunning plan for Detective Sunday is to recruit the rather excellent Brenda Blethyn to play DCI Vera Stanhope in adaptations of Ann Cleeves's novels, set in the author's native North-East.