- Video report by ITV News Anglia's Dani Crawshaw
On the fiftieth anniversary of the murder of an Air-craftswoman from Stevenage Thames Valley Police have launched a fresh appeal to help solve the case.
19-year-old Rita Ellis was murdered at RAF Halton in Buckinghamshire in 1967. She was found beaten and strangled close to where she worked.
Her killer has never been found, but now detectives are hoping advances in DNA techniques will finally help get justice for her family.
Rita's sister, Tina Streeter, was 10 at the time, she said: "I remember my mum screaming, crying - I didn't see her for a little while. My older brother Geoff came and told me and I was trying to take it in, I thought no it's nonsense - I did understand but I didn't really want to understand - it was a strange time."
On the night Rita was killed she was due to babysit for a wing commander near to the RAF base, but she could not be found. The last time she was seen alive was around 8pm.
Rita's body was found the next day by a dog walker about 300 yards behind what used to be a coal yard. At the time it was Scotland Yard that began the investigation - 50 years on it is Thames Valley Police that are now investigating - they believe someone knows something.
Thames Valley Police Major Crime review team reopened the case tens years ago. Officers now have a full DNA profile of the offender - and have ruled out over 200 potential suspects.
Peter Beirne, Principal Investigator at Thames Valley Police is hopeful they will find Rita's killer. He said: "Rita's parents died not knowing who was responsible, she has a sister - two brothers - it's important for them to know that her death isn't forgotten and that the police are still interested in her death - and we are doing all we can to bring the offender to justice."