I follow this case off and on, but rarely post. I'm not familiar with that area of the UK having only been to Scotland so there is little I can contribute. I did find the statement by the senior investigator to be interesting. "Several" persons know or suspect what happened to her. Not 'a person', but 'several'.
Joan Lawrence will ‘never give up on hope’ that mystery of 35-year-old going missing in 2009 can be solved
www.theguardian.com
It makes me wonder what he has come across that has led him to multiple persons. The more people who know the harder it is to keep a secret. Makes me think of one case here in the US. Lauria Bible and Ashley Freeman in 1999. There wasn't an arrest till 2018, but afterwards it was learned that several persons heard who did it and that there were even photos of the girls before they were murdered. People had known or suspected for years before the arrest. Granted this is small town USA in Oklahoma and not North Yorkshire UK. But I do wonder what an experienced investigator in North Yorkshire has come across to lead him in search of multiple parties.
en.wikipedia.org