Plans to seize Julian Assange “under all circumstances” the moment he leaves the Ecuadorean embassy in London have accidentally been revealed by a police officer displaying restricted documents outside the embassy.

The document, pictured under the officer’s arm by a Press Association photographer, appears to advocate arresting the WikiLeaks founder whether he leaves the building in a diplomatic bag or in a diplomatic car.

The handwritten plan was recorded at a police briefing and only partially covered by the officer’s arm as he arrived at the embassy in Knightsbridge on Friday.