One thing I'm left puzzling over is the jury's verdict on Mark. I'm really surprised they bought the personality disorder theory, given that the prosecution did a pretty good job of discrediting the young psychologist's PHD.
Who says they bought the personality disorder? He got 10 years, reduced to 5 ( for good behaviour?), so 10 years for manslaughter is par for the course.
I think too many people are reading too much into it all, based on the TV series. At face value, he wasn't as clever as he thought he was.
The CCTV may or may not have been connected; obviously he said it wasn't at the time to placate her, regardless of what he really thought or knew- but the evidence of their shag came from somewhere.
I don't think she played him. I think she simply said what she was thinking at the time re. killing George, but didn't for a minute think he would act on it. If she really thought he was MI5 it may have been said as a 'joke' and she didn't think he'd do it.