Alice Chambers, a 36-year-old architect, was handcuffed and held for 13 hours after being mistaken for a Just Stop Oil protester during the King's Coronation. She was detained on the Mall despite showing ID and explaining she was a royal fan.
Ms Chambers told BBC Newsnight she was arrested alongside protesters, then fingerprinted and questioned at a police station. She missed the entire Coronation celebrations and has lodged a formal complaint against the Metropolitan Police.
The Met said the arresting officer was from Lincolnshire Police and has passed the complaint to them. Lincolnshire Police confirmed they are reviewing the incident and are in contact with Ms Chambers.
The arrest is one of 64 made during the Coronation policing operation, with 52 related to concerns about disruption. The Met previously expressed regret over the arrest of the head of anti-monarchy group Republic.
