The sentences are the longest since the introduction by the last government of the new law of conspiracy to cause a public nuisance, in a bid to clamp down on disruptive protests.

The court heard the intention was to block most of the M25, preventing traffic from other roads from joining the motorway.

The action resulted in chaos on the M25 over four successive days, causing nearly 51,000 hours of driver delays, the court heard. The protests closed parts of the motorway in Kent, Surrey, Essex and Hertfordshire.

People missed flights, medical appointments and exams. Two lorries collided, and a police motorcyclist came off his bike during one of the protests on 9 November 2022 while trying to bring traffic to a halt in a “rolling road block”.

A Zoom call chaired by Shaw was infiltrated and recorded by a Sun newspaper journalist and passed to the police, the court heard.

Judge Hehir said the recording revealed the “intricate planning and the level of sophistication involved” in the protest action.