cops gave permission for a movie gun battle in London -- then later declared it a crime scene when a member of the public found bullet casings

Keystone cops gave permission for a movie gun battle in London -- then later declared it a crime scene when a member of the public found bullet casings, The U.K. Sun reported.

Amazingly, they failed to link the incident to a film crew who hours earlier fired 1,700 blank rounds for a scene in gang flick "The Veteran," starring Toby Kebbell, 28, as a soldier who turns to crime.

Two cops were present during three days of action, then production staff swept up the empty shells. But next morning, police were alerted to suspected gun activity on the Heygate housing project in Elephant and Castle, south London.

Forensic experts combed the streets and found some bullet casings, but it was not until the next day that tests revealed they were blanks.

"It is astonishing the police could not tie the two together," said a spokesman for entertainment rental firm Foxtrot, which supplied guns for the filming.

He said cops even suggested the firm could be charged with wasting police time.

A police spokesman said the casings were "confirmed to be blanks" and inquiries were ongoing.

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