Met Police Detectives have announced a £40,000 reward to help solve the 1975 murders of Eve Stratford and Lynne Weedon.
Relatives joined them in a special feature on BBC Crimewatch urging witnesses to come forward.
The reward is for any information leading to the identification, arrest and prosecution of the person or people responsible for the killings.
The murders of Eve in Leyton and Lynne in Hounslow remain unsolved despite extensive enquiries but officers hope the passage of time may now encourage someone to come forward with information.
The murders were linked in July 2006 after a review and advances in technology determined that the same DNA had been found on both victims.
Investigating officer Detective Chief Inspector Noel McHugh, from the Homicide and Major Crime Command said he was hopeful the killer had let details slip over the years – maybe to a partner, a friend or even a cellmate or medical professional. The complex and length DNA work continues.
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