Lewisham Hospital staff have been warned when walking through a nearby park following reports of attempted robberies in the daytime.
Police contacted Lewisham and Greenwich NHS last week, urging health workers to be careful if they visit Ladywell Fields, which is just behind the hospital.
There has been a spate of attempted robberies between midday and 4pm. Reports suggest the suspects are carrying knives.
Extra police officers are patrolling the area, but NHS workers have been told be on guard.
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