The record jail sentence for the co-founder of Just Stop Oil could serve as a "rallying call" to other climate activists for a wave of protests, police believe.
Roger Hallam, 58, was jailed for five years on Thursday for orchestrating protests that disrupted the M25 over four days in November 2022 when 45 protesters climbed gantries on various parts of the motorway, forcing police to stop traffic.
Daniel Shaw, 38, Lucia Whittaker De Abreu, 35, Louise Lancaster, 58, and Cressida Gethin, 22, were each given four years after being found guilty along with Hallam of conspiracy to cause a public nuisance.
The sentences, handed down by Judge Christopher Hehir, are thought to be the longest ever given for peaceful protest and have been widely criticised.
Detective Inspector Chris Rudd, who led the investigation, said there were "certainly signals from the [activist] groups" that they intended to stage a protest in retaliation to the sentences.
He told The Times: "The judge commented upon sentencing that he hoped it may have some deterrent effect on others that wanted to cause serious disruption to members of the public. I do hope it does have some deterrent effect. But for some, it might be a rallying call."
The five Just Stop Oil activists were recorded by an undercover reporter for The Sun during a Zoom call in which they discussed the planned protests and were aiming to recruit others.
Rudd said the protesters were known to police before the covert recording. "The call contained compelling evidence of them engaging in a plan to conduct what is criminal activity. They wanted to cause absolute gridlock and chaos."
The court was told that the M25 protests delayed more than 700,000 vehicles and caused economic damage of £765,000, and the cost to the Met was more than £1.1 million.
Lord Falconer of Thoroton, the former justice secretary, said the sentences make him feel "very uncomfortable," noting "these are people who are not violent criminals."