Who killed Holocaust survivor Emmy Werner in 1972? The Met Police is on a mission to find out.
Detectives are launching a fresh appeal regarding the murder of Werner, killed in Bayswater, London on 17 September 1972. They are offering a £20,000 reward for anyone with information that could lead to the "arrest and prosecution of the killers".
Werner's body was discovered in her room by a chambermaid at Queens Hotel. She had been strangled and suffered several other injuries, possibly defensive wounds.
Within a few weeks of the murder, a 16-year-old boy was arrested, but he was later acquitted in 1973.
On the night preceding her murder, Emmy had been to the theatre with friends. She came back to the Queens Hotel, Inverness Terrace, at around 8.30pm.
Police believe she was attacked in the early hours of 17 September. The most likely motive appears to be theft. Detectives think the attacker entered her room to steal money, but woke Emmy up in the process.
They are now hoping that people who working at the Queens Hotel or visiting at the time have useful information.
"Although many years have now passed since Emmy's death it remains particularly difficult for her family that she survived the horrors of the Holocaust yet died in such brutal circumstances,"Met detective Inspector Susan Stansfield said.
Stansfield adds that several guests and staff members talked to police forces back in 1972, but she hopes that the passage of time will help solve the case.
"It is possible that the events of that night have since been discussed and there is information that could be really useful to our inquiry. Or maybe someone who was scared to speak to officers at the time might now feel able to come forward."
Police are particularly keen on talking to the two friends Emmy went to the theatre with, two women, one of whom was also a guest at the Queens Hotel.
Carolyn Franks says that nobody should die the way her grandmother Emmy did: "The effect on her close family continues to be a source of great sadness to us and we feel whoever killed her should be held to account."
Born in Czechoslovakia, Werner had lived a happy life in Brno with her husband Albert. However, in 1942, three years after the start of the Second World War, their family and other relatives were deported to Theresienstadt, a concentration camp located near Prague.
As the Allies advanced on the Axis forces, Albert was sent to Auschwitz, and was eventually killed by the Nazis in Kaufering in 1945.
Emmy and her daughter Hedy were liberated in May 1945, and settled in London in 1946 where they had a new family. They both lived in Finchley.
Emmy had been traumatised by the horrors of war, but she was making progress through treatment.
She visited her sister regularly, in Central London. She would always stay at the Queens Hotel, Inverness Terrace.