A knife-wielding teenage girl threatened a shopkeeper during an attempted hold-up in Mitcham.
Police said the girl pulled a large knife on a 34-year-old shop assistant at Corners Off Licence in Mitcham.
The robber left the shop empty-handed after the frightened assistant triggered its alarm system.
Detective Constable Riaz Karolia of Wimbledon CID said: "This was a random attempt to scare a hard working shopkeeper and steal their money.”
The attempted robbery happened at about 5pm on February 7.
D Con Karolia asked anyone with information about the robber, a white teenage girl thought to be aged 16 to 18 and seen wearing a black hooded jacket on the night of the crime, to call Crimestoppers in confidence on 0800 555 111.
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