The detention of the Republic protestors at the coronation is reported so:
At around 6am on the morning of the coronation, Smith and his colleagues brought down the amplifiers and megaphones from their Premier Inn hotel on St Martin’s Lane to Trafalgar Square. Then they returned outside the hotel to unload a large rental van full of placards. “I managed to get one of those bundles out onto the tailgate and I turn around and these police officers come in, three or four of them, but then all of a sudden all the others come out of a van, wanting to know what we were doing.”
Smith was ushered away from the van. It was about 6.40am. “I said: ‘We have been talking to senior officers.’ And he said: ‘Who?’ And I said: ‘Mr. Kirby’, and he clearly recognised that and seemed a bit disappointed. And then I went to phone the liaison officer. And he said: ‘I’m now detaining you,’ and I went: ‘I’m just gonna stay on the phone.’ He just said: ‘What are you doing? I’m detaining you.’ And he just grabbed my wrist and took my phone off me.”
Plastic packs were also found in the van containing 10 adjustable luggage straps, the type to keep bulging suitcases together, but which Smith was going to use to hold the placards onto trolleys as they were pushed down to Trafalgar Square. He was arrested for possession of lock-on devices and then all six of his group were put in a police van and taken to Walworth police station, in Kennington.
The initial detention occurred sometime prior to the discovery of luggage straps, therefore the initial detention cannot have been an arrest. The other form of detention I am aware of is stop and search. The legality of this seems to be defined/ensured by the GOWISELY acronym, described by the police here and few elements are present, in particular the information that must be provided and the use of force which must be used only as a "last resort" if absolutely necessary.
Under what powers were the Republic protestors detained and "use of force" used during the coronation?
For information, this is what he was arrested for and this is how many staff they had to provide any required information.
