I'd never heard of Lesley Hobbs, but had heard of Maureen Dutton. I've just googled and found out a little about her. God she was only 12yo. The file is closed (National Archives) for 85 years but it did name her killer, who had mental health problems by the sounds of it "diminished responsibility". He was also suspected of being the killer of Mrs Dutton, which I didn't know.

Why are files closed for so long? It's nearly 50 years since the murders, I'd have thought around 30 years would be nearer the mark.