Twelve Just Stop Oil protesters have appeared at the High Court accused of breaching an injunction aimed at restricting protest on the M25 and causing “the maximum disruption possible to the general public”.

National Highways is seeking to have the environmental activists found in contempt of court after they climbed on to gantries and caused “considerable delays” on the UK’s busiest motorway in November last year.

At a hearing in London on Monday, the Government agency said its case came after a “concerted campaign” by Just Stop Oil (JSO) to “cause gridlock” on the M25.

The protesters do not dispute scaling the gantries, but some contested the alleged breach claiming they had no knowledge of the November 2022 civil court order and should not be held in contempt nor penalised.

The group of 12, Charlotte Kirin, 54; Daniel Johnson, 25; Gaie Delap, 76; Joseph Linhart, 22; Luke Elson, 30; Mair Bain, 36; Paul Bleach, 56; Paul Sousek, 72; Paul Bell, 23; Rosemary Jackson, 25; Theresa Higginson, 25; and Theresa Norton, 65, attended the hearing before Mr Justice Soole in the Royal Courts of Justice.

People who breach injunctions can be found in contempt of court and face a maximum penalty of two years in prison or an unlimited fine.

Michael Fry, for National Highways, told the hearing that the injunction came after an investigation by The Sun newspaper infiltrated a JSO training session.

Videos of protest plans were shared with the police and National Highways – the Government-owned organisation responsible for England’s motorways and major A-roads – and the injunction was sought, the court was told.

Mr Fry said in written arguments that video evidence showed “an immediate risk of trespass to the M25”, with JSO having plans “to escalate their protest activity by placing activists on gantries evenly spaced across the M25” and to “cause gridlock across the whole of the M25”.

He added that “the protest caused considerable delays to traffic and caused public disruption” after a “deliberate flouting of a court order”.

“The order prohibited the defendants from carrying out a protest by climbing structures on the M25,” Mr Fry said.

The barrister said the group of activists “chose to defy the order and impose their own views of what level of inconvenience and harm the public should have to put up with” and “broke the social contract under which in a democratic society the public can properly be expected to tolerate peaceful protest”.

“This is a case where the defendants have taken it upon themselves to protest on gantries in order to cause the maximum disruption possible to the general public,” Mr Fry said.

He said that there was “no doubt” that JSO was aware of the order before the protests and that the court “can be sure” activists were aware the M25 was protected by an injunction.

Owen Greenhall, representing the activists, said in written arguments that they had climbed the gantries between November 7 and 10 last year as part of a “peaceful protest”.

“It is not in dispute that the defendants each climbed on gantries on the M25 motorway and that these acts were contrary to the terms of the injunction order,” Mr Greenhall said.

But the lawyer added that those defendants without knowledge of the injunction “should not be held liable for contempt and in any event no penalty should be imposed”.

He said: “In any event, the conscientious motivation of environmental protesters is a very strong mitigating factor in the sanctions to be imposed for any findings of contempt.”

Mr Justice Soole gave a preliminary ruling in favour of National Highways at the end of Monday’s proceedings, finding that “actual knowledge” of an injunction was not a “necessary ingredient” for someone to be liable for contempt.

The hearing, which is expected to last four to five days, is next due to hear arguments over whether or not the protesters were in contempt, and if they were what potential sanctions could be imposed.