The Metropolitan police have defended the arrest of anti-monarchy protesters during the coronation despite announcing that no charges will be brought against them.
The force said it expressed “regret” that six demonstrators from the Republic campaign group were arrested on Saturday.
Graham Smith, the head of the group, said it was considering legal action and demanded an inquiry into the conduct of officers.
Scotland Yard released a statement on Monday night stating that it believed items found alongside a large number of placards could be used as “lock-on devices”.
“The investigation team have now fully examined the items seized and reviewed the full circumstances of the arrest,” the statement added. “Those arrested stated the items would be used to secure their placards, and the investigation has been unable to prove intent to use them to lock on and disrupt the event.
“This evening all six have had their bail cancelled and no further action will be taken. We regret that those six people arrested were unable to join the wider group of protesters in Trafalgar Square and elsewhere on the procession route.”
Smith said a chief inspector and two other officers from the Met apologised to him at his home in Reading on Monday evening.
The activist told the PA news agency: “I had three officers at my door personally apologising and handing the straps [for the placards] back to me. They were a chief inspector and two other officers from the Met. They seemed rather embarrassed, to be honest.
“I said, ‘For the record, I won’t accept the apology. We have a lot of questions to answer and we will be taking action.’”
Smith wrote on Twitter: “This has been a disgraceful episode and we will be speaking to lawyers about taking legal action. I also expect a full inquiry into why they repeatedly lied to us and who authorised the arrests.”
Earlier on Monday, Smith said the arrests were a premeditated attempt to “disrupt and diminish” the republican demonstration and that the police’s decision to break up the planned protest before it began trampled over their rights. He added the group had been in conversation with Scotland Yard for months before the event.
It came as City Hall politicians joined the London mayor, Sadiq Khan, in seeking answers from Scotland Yard over the detention of Republic protesters and volunteers working for the local council to keep people safe.
Smith told BBC Radio 4’s Today programme on Monday morning: “We have had four months of close conversation with the Metropolitan police, in which we have explained to them exactly what we’re going to do, where we’re going to be. We told them how many placards we had, what they would say, that we would have flags, that we would have amplification equipment.
“The amplification equipment was then seized and my colleagues were told they’d be arrested if they used megaphones. The whole thing was a deliberate attempt to disrupt and diminish our protest.”
Asked if he thought his arrest before the event was premeditated, Smith said: “Absolutely. I have no doubt about that at all.”
He said his organisation had engaged with the police throughout the planning of its demonstration, and that officers had said until the day before that they had no concerns.
The Met said it arrested 64 people on Saturday, including members of Westminster city council’s women’s safety campaign Night Stars, who hand out rape alarms and other items. Police claimed intelligence had indicated that people were planning to use rape alarms to disrupt the coronation procession.
Scotland Yard faces scrutiny over its handling of the event, with the Green politician Caroline Russell, who chairs the London assembly’s police and crime committee, calling it “really worrying”.
She told Today: “It felt like, for someone who was trying to protest and trying to do it by the book, it was very difficult to understand what the rules were.”
Rishi Sunak backed the police on Monday, saying: “The police are operationally independent of government – they will make these decisions based on what they think is best.
“Actually, I’m grateful to the police and everyone who played a part in ensuring that this weekend has gone so well, so successfully and so safely. That was an extraordinary effort by so many people and I’m grateful to them for all their hard work.”
The mayor of London said on Sunday: “Some of the arrests made by police as part of the coronation event raise questions and, while investigations are ongoing, I’ve sought urgent clarity from Met leaders on the action taken.”