A foot chase saw Hornchurch police officers take a knife off the streets, but the suspect got away.
On January 15, officers from Elm Park and St Andrews safer neighbourhood team were on patrol as part of a week of action.
While patrolling Hornchurch Town Centre, officers went to stop a "male" they alleged was smoking cannabis.
A Met Police spokesperson said: “On this male seeing that we were police officers, he ran away.
“A foot chase started and the male threw a knife on the floor.”
Despite a search, Scotland Yard said the suspect got away.
They added: “However, enquires are being made to establish the ID of the male by forensics of the knife and local CCTV.
"Hopefully he will be arrested at a later date.”
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