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The British ambassador to Iran, Robert Macaire, is arrested during anti-government protests, after attending a vigil and then, according to BBC, getting his hair cut. According to Tasnim News Agency he was arrested "on suspicion of organising, provoking and directing radical actions". U.K. Foreign Secretary Dominic Raab states the arrest is in "flagrant violation" of international law. More than an hour later, Macaire is released from custody.

British ambassador arrested at Tehran demonstration

Sources:  The Guardian