Protesters appear to have been arrested ahead of the King's coronation.
Footage on Twitter seemed to show Graham Smith, chief executive of the anti-monarchy group Republic, being apprehended by police in St Martin's Lane, near Trafalgar Square, on Saturday morning.
Pictures appeared to show demonstrators in yellow "Not My King" T-shirts, including Mr Smith, having their details taken by officers.
In one video, an officer says: "I'm not going to get into a conversation about that - they are under arrest, end of."
