Detectives have announced a £40,000 reward to help solve the brutal 1975 murders of Eve Stratford and Lynne Weedon.
Investigators said, on BBC Crimewatch on Thursday (April 23), the reward is for any information leading to the identification, arrest and prosecution of whoever is responsible for the killings, as they hope the passage of time may now encourage someone to come forward.
Eve died of neck injuries on March 18, 1975, aged 21. She was last seen by witnesses walking alone near her home in Lyndhurst Drive, Leyton, at around 4pm.
Just 30 minutes later, an occupant in another flat at the converted house in Lyndhurst Drive heard the voices of a man and a woman talking, not in a heated or confrontational manner. short while later, however, the witness recalled hearing a loud thud noise coming from Eve's first-floor flat. Her body was discovered by her boyfriend at 5.20pm in the bedroom.
The 21-year-old victim, who worked as a bunny girl, had a nylon stocking tied round one ankle and a scarf round her hands. Her neck had been cut between eight and 12 times.
A post-mortem examination held gave cause of death as knife wounds to the throat.
There was no sign of forced entry to the flat and no weapon was ever recovered.
On September 3, 1975, at around 11.20pm, 16-year-old schoolgirl Lynne was raped and murdered near her home in Hounslow.
Lynne had been walking home after an evening out with friends and detectives believe she was followed from Great West Road (the A4) into an alleyway called The Short Hedges where she was hit with a blunt instrument and thrown over a fence into the grounds of an electricity sub-station. She was then raped before the suspect left the scene.
Lynne was discovered by a local school caretaker whose house overlooked the sub-station. Despite the horrific nature of her injuries, she was still alive when police and paramedics arrived at the scene.
However, she never regained consciousness and died at West Middlesex Hospital a week later. The cause of death was a single blow to the head - her skull had been smashed with a heavy blunt instrument, which was never recovered.
It is likely the suspect for both murders is now in his 60s or 70s.
Detectives are keeping an open mind but have previously said it is possible the killer knew his victims, particularly Eve who had a huge circle of friends and acquaintances.
It is also thought the murderer had knowledge of the Hounslow area - the alleyway and sub-station are away from busy areas and would have meant Lynne's screams or struggles would most likely have gone unheard.
It appears the motive was sexual - Lynne had been raped and it is likely Eve had also been raped although officers have not been able to rule out consensual sex.
Last month, the Met issued a renewed appeal for information on the 40th anniversary of the killings.
Anyone with information is asked to call the incident room on 020 8785 8099 or Crimestoppers anonymously on 0800 555 111.