British police have arrested Graham Smith, the leader of the anti-monarchy group Republic, on the eve of the coronation of King Charles, a spokesman for the group said, quoted by Reuters.

London’s police chief, Mark Rowley, warned on Friday that there would be a “very low tolerance for disorder” on the streets of central London, where tens of thousands of people have gathered to watch the royal processions.

The police did not confirm the arrest.

In a photo posted on Twitter, Smith is sitting on the ground surrounded by a group of police officers. An officer at the scene near Trafalgar Square said three republican protesters had been arrested for the paint.

More than 11,000 police are patrolling the coronation, the biggest ceremonial event held in the British capital for 70 years.

Ahead of the event, Rowley said police would take action if protesters tried to “disrupt the joy and celebration” of large numbers of people.