Coronation protesters ARRESTED in central London after plot to disrupt King's big day with megaphones and placards

Footage on social media appeared to show Graham Smith, chief executive of the anti-monarchy group Republic, being apprehended by police in St Martin’s Lane, near Trafalgar Square.

About half a dozen protesters were detained by police while they were unloading placards from a van.

Group spokesman Luke Whiting, 26, said: "Six Republic members have been arrested including the CEO as the demonstration was starting at the edge of Trafalgar Square.

"It is unclear why, potentially it is because one of them was carrying a megaphone.

"It is unclear exactly whether the police are using these new powers and whether they are misusing them to stop protest happening."

Republic says it thinks police misunderstood the nature of their protest.

It believes police thought the group intended to copy the extreme tactics used by eco-activists.

Extinction Rebellion members have become known for using strapping to tie themselves to objects in order to cause maximum disruption.

Republic say the strapping police confiscated during the arrests was for banners.

One woman in a Republic T-shirt who was arrested said: “We had a delivery of placards ready for the protest and then the tactical support unit questioned us as to how we we had got through the road closures.

“They questioned whether what we were doing was a delivery.

“They then said they found evidence of means of locking on, of items that could be used to lock on, and they arrested us.”

Officers carried her away from where she had been standing outside a Tesco store.

Two men who appeared to have been part of the same demonstration were carried away by officers into a marked police van.

A last minute change to the Coronation service was made last night amid fears that an "oath of allegiance" planned for the ceremony would spark anger and lead to a rise in anti-monarchy sentiment.

Britons will now be "invited" to take part in a "homage of the people" instead.

Police had warned protesters run advance on today's event that they would take no chances when it came to protesters.

The Met Police said: "Our tolerance for any disruption, whether through protest or otherwise, will be low.

"We will deal robustly with anyone intent on undermining this celebration."

There are as many as 11,500 police officers on duty today to ensure events go smoothly and without disruption.