Was very disappointed myself, Nick.
After a gritty, realistic start from the first 2 episodes, the final part seemed to get rather silly I felt, with people suddenly spilling the beans left right and centre for no particualr reason and it all pushing the bounds of realism to the extreme.
I couldn't stop laughing at the scene in the interrogation room. Doubt had been cast as to whether John Simm's character had actually done it.
When the coppers had the actual perpretator of the murder in custody and were interviewing him, the lad said that John Simm's character accidently pushed his son down the stairs and then went into the lounge, fought with is wife and stabbed her. Amazing all this, as he said he was hiding in the bedroom the whole time.
The coppers just accepted his story without any cross examination and simply just started looking for John Simm's character again for the crime.
Was a shame as I had really enjoyed it until about 15 mins in and then I found it all get rather OTT and silly.