Emily Armstrong (c. 1880 – April 14, 1949) was a British victim of an unsolved murder in which she had been beaten to death and later found at her place of employment, a dry cleaner's shop on St John's Wood High Street. Police later determined she had been killed roughly an hour before her body was found at around 4:00 pm. A postmortem examination also showed that her skull had been shattered by at least 22 blows from a blunt object, later believed to be a claw hammer.
Although her handbag had been missing at the scene, it was later found nearby with a bloody handkerchief bearing a laundry mark H-612, although no leads resulted from that piece of evidence.
While authorities pursued several theories, they failed to find a suspect. Witnesses reported a "suspicious man" around 30 years old and between 5'5" or 5'6", however, police were unable to identify the individual. A murderer who had recently escaped from Broadmoor hospital was also considered before witnesses failed to identify him in a police line-up. Several army deserters were also questioned, however, all were eventually released.
One possible theory suggested a link to a similar murder which had taken place ten years previously when 65-year-old Gertrude O'Leary was found beaten to death on June 30, 1939; although no known connection has been proven.
Police eventually concluded that Armstrong's murderer had either been a transient or "a man who had fled to Ireland."