This comment stream on the Fortean Times message board mentioned the Hackney bear story as if it was common knowledge. All I could find were these 1981 reports from US-based newspapers - none from UK papers which may not have uploaded their archives from that far back. But reports - like this one - describe a hoax that went worldwide.
According to these old cuttings, the bodies of two headless bears were found in a Hackney canal and then a real live bear scared kids playing on Hackney Marshes.
The cuttings say that the search for the bear was called off after a guy called Ron told the The Sun that he was the bear. He said that the discovery of bears' bodies (it was later suggested that these may have been dumped in the canal by a travelling circus) inspired him to dress up as bear and roam about on Hackney Marshes. The result was an invasion of police and army marksmen and a helicopter. No bear was found although tracks were allegedly discovered. Ron, it seems, was never caught. Is any of this true?
The myth lives on: The Bear of Hackney