WPC Tomlin was the London police constable in charge of the investigation when Elsie Howard was hit by a car in 1973. Elsie had been returning to Berkeley Square to retrieve her handbag which she had absentmindedly left on a bench there when she was struck by the vehicle, and so wasn't carrying any identification when she was taken to hospital.
As Elsie remained unconscious for some time, Tomlin was concerned mainly with identifying the mystery woman. Her investigation took her to the shop where Elsie had bought a present for Alan, but she obtained no new information from the staff there. She later submitted her description to the local missing persons lists, which resulted in a man whose wife had gone missing coming in to identify her, although it turned out to be a false alarm.
A breakthrough was made when Nurse Maclean made a note of phrases Elsie had repeatedly uttered in her sleep - "double glazing", "Pentonville", and "Dennis Tanner", and passed these onto WPC Tomlin via Sister Delaney. Tomlin was then able to piece together the fact that Elsie had come down from Weatherfield to visit Dennis at Pentonville Prison, and got onto Weatherfield Police Station who made the connection with a woman recently reported missing there. Elsie woke up soon afterwards and filled in the missing information herself. Tomlin then closed the case, concluding that there were no suspicious circumstances involved.