National Highways is preparing to take up to 50 Insulate Britain protesters to court after they defied an injunction banning them from the M25.

       A source said the agency now had the names of protesters and would serve the injunction on them which carries a maximum penalty of two years in jail and/or unlimited fine for breaches of it.

       Nicola Bell, regional director of National Highways, refused to comment on the specifics of the action, but said: “We are in the process of taking legal advice, and we will look to pursue those who repeatedly offend.

       “The injunctions now in place are designed to put an end to dangerous and disruptive protest activity, and people who breach these injunctions face prison or an unlimited fine.”

       The move came after all the 53 climate activists who blocked the M25 at junction 14 on Monday were released under investigation by the Metropolitan Police.

       It was the sixth time in two weeks that they had blocked the M25, see picture below, and was in violation of the High Court injunction that puts them at risk of imprisonment, a fine or having their assets seized.

       No protesters were named in the original injunction, nor have they had it served on them.

       Instead, National Highways has relied on a legal device that publicity around the injunction means the protesters would have known they were liable and were covered by it.

       Mark Stephens, a litigation specialist at London-based Howard Kennedy LLP, said that to enforce the injunction, National Highways would now have to show not only that the protesters breached its terms but that they also had notice of it.

       “The difficulty is that sometimes these injunctions are obtained too randomly and without the appropriate balances in them,” he said. “You cannot just take away someone’s right to demonstrate.”

       In an open letter to Priti Patel, the Home Secretary, Insulate Britain vowed to continue its campaign in the face of arrests and injunctions. It said: “We are more fearful of the loss of our country than we are of you.

       “You can throw as many injunctions at us as you like, but we are going nowhere. You can raid our savings. You can confiscate our property. You can deny us our liberty and put us behind bars.

       “But shooting the messenger can never destroy the message: that this country is going to hell unless you take emergency action to stop putting carbon into the air.”

       Following the release of the 53 people from police custody, a Department for Transport spokesperson said: “The right to protest is a fundamental principle of our democracy, but we will not tolerate the guerrilla tactics we have witnessed over the past two weeks.

       “That is why we sought injunctions to put an end to this behaviour, which wreaks havoc and puts people’s lives in danger.

       “These injunctions are now in place, meaning that if people protest, or encourage others to do so, they face prison or an unlimited fine.”