So the wife never thought to mention she woke up to find Lucas had broken in and stood at the bedside with a knife once before? Seriously?
I've watched 31 episodes of L&O:UK now and I don't think I've ever had a bigger WTF moment. Her ex, who she was afraid would do something violent, with a knife, murderers two people, with a knife, and she NEVER mentions it to the police? I'm sorry, but that is just plain bad writing. Unless they wanted to set up she was actively trying to protect her ex, which they didn't do.