Sixteen environmental activists jailed in the past year will appear at the high court on Wednesday to ask England’s most senior judge to quash their “unduly harsh” sentences.The appellants, from four separate cases, will appear before a bench of judges led by Lady Carr, the Lady Chief Justice, in a full session of the court of appeal in which they will argue that judges defied decades of precedent to hand them long jail terms for nonviolent protests.A host of celebrities are expected to join hundreds of protesters outside, while Greenpeace and Friends of the Earth are lending their legal expertise in court to support what they describe as a “crucial legal test over the right to protest”.Supporters say the appellants’ sentences, ranging from 20 months to five years for a range of nonviolent civil disobedience protests, are excessive and disproportionate, and the result of a politicised crackdown that is stifling to democratic rights.The sentences up for appeal include the five-year jail term handed to Roger Hallam, the co-founder of Extinction Rebellion and Just Stop Oil, for taking part in a Zoom call planning road block protests on the M25; three years given to Larch Maxey for occupying a tunnel outside an oil terminal in Essex in 2022; and two years imposed on Phoebe Plummer for throwing tomato soup on the glass-covered Sunflowers painting by Vincent van Gogh at the National Gallery.Also among the appellants is Gaie Delap, 78, who was recently recalled to prison because government contractors were unable to find the right-sized tag for her wrist.Supporters have nicknamed the group the “Lord Walney 16”, pointing out that their long sentences all came after the crossbench peer Lord Walney, who was appointed the previous government’s adviser on political violence, published a report calling for groups such as Just Stop Oil and Extinction Rebellion to be relabelled “extreme protest groups” and subjected to stringent restrictions like those applied to terrorist organisations.It is highly unusual for the court of appeal to combine applications from so many different cases, a decision that observers say highlights the significance of the case. However, Carr previously upheld long sentences for two Just Stop Oil protesters who blocked traffic on the QE2 motorway bridge over the Thames, arguing they were justified as “a deterrent” to others thinking of taking part in similar protests.Zoe Cohen, an Extinction Rebellion spokesperson, said: “Every citizen should have the right to effective protest. It’s a crucial part of democracy. These excessive sentences are designed to put people off protesting. But the laws that enable these sentences were written by thinktanks that are funded by the corporations, oil money and the obscenely rich – the same actors who are responsible for brutal inequality and driving us to extinction.”Greenpeace and Friends of the Earth have been granted permission to intervene in the appeal specifica