Twenty-one people arrested on the day of the King’s Coronation to prevent potential disruption from protests will face no further action.
The Metropolitan Police said the Crown Prosecution Service had reviewed the evidence and concluded there was “no realistic prospect of conviction”.
The force said groups were arrested in order to prevent a breach of the peace and on suspicion of conspiracy to cause a public nuisance in The Mall and in Whitehall on May 6.
Officers from the Met Police referred the cases to the CPS in August 2023.
Mr Twist said: “We had real concerns that such efforts would not only disrupt a once-in-a-lifetime event of enormous national significance, but that they could also compromise the security and safety of participants and the wider public.
“Officers were briefed on these concerns and we needed to be proactive in managing this risk and prevent any activity that could put public safety or the security of the event at risk.”
The assistant commissioner said the Met Police had an extensive policing plan in place to ensure people could protest peacefully.
Protests were held along the procession route, including in Trafalgar Square.
“Every day officers have to make difficult decisions with limited time, based on the often partial information, and I support them in their decision making in this case.
“For example, three of those who were arrested on the day which did not lead to charge, were found near the Coronation route in the early hours of the day of the event in possession of glue, a banner from a known activist group, Allen keys and other paraphernalia that could have been used to commit criminal damage or other disruption.
“I am confident the public would recognise why officers chose to make arrests in such circumstances, even though it has ultimately been determined that a conviction at court would be unlikely.”
Graham Smith and five other members of the group were held on suspicion of going equipped to lock on – a tactic some protesters use to make themselves more difficult to move on – because they had luggage straps to secure their placards.
On May 8 they were told no further action would be taken.
Republic chief executive Mr Smith told the PA news agency he was “pleased the others are not being charged”.
He said: “The Met needs to learn a lesson about not over-policing protests and make sure protesters are allowed to go ahead peacefully.
“There needs to be action taken against the police. They can’t be allowed to simply shrug it off and move on.”