The group were taking part in a non-violent protest against climate change and the pollution caused by the giant coal-fired Drax power station, near Selby, in June last year.

Judge James Spencer QC, sitting at Leeds Crown Court, told the defendants they would not be going to jail and adjourned sentencing until September.

Five other defendants pleaded guilty to obstructing the railway and two others have indicated in writing that they will also admit the offence.

The trial, which was scheduled to last two weeks but only ran for four days, heard how the train was stopped by two men posing as Network Rail staff, wearing orange jackets and hard hats, who held up a red flag.

Moments later the train and a nearby bridge were scaled by the protesters wearing white paper boiler suits and carrying banners.

The protest lasted 16 hours, causing delays to numerous freight and passenger services and the clean-up operation cost more than £30,000.

None of the defendants denied being on the train but they told the jury they did not believe they were doing anything criminal because they were trying to prevent climate change.

Rob Turnbull, chief crown prosecutor for North Yorkshire, said the protesters committed "a well planned and executed crime".

"This was not a peaceful demonstration about the environment, but a well planned and executed crime where two defendants impersonated railway employees and went on to the trackside to stop a train lawfully delivering coal to the power station.

"The rest of the group, who took control of the engine and train, attached lines to the wheels to stop the train moving and unloaded coal off the train."

He added: "There was legal argument before the trial started on whether the protesters could claim a defence which is known as 'duress of circumstances' or necessity, where someone commits a criminal act to prevent a greater criminal act being committed.

"The protesters also wanted to call experts on global warming to underline the consequences of burning fossil fuels.

"After hearing from both the prosecution and the defence, the judge ruled that this defence was not available to the defendants as they were in no immediate danger and nor was anyone else, and consequently evidence from the experts should not be allowed.

"The right to protest is an important aspect of a democratic society but when people cross the line into criminal activity they should be aware they may well find themselves facing prosecution."

The 22 defendants found guilty today are:
Theo Bard, 24, of Chepstow Villas, Notting Hill, London
Paul Chatterton, 36, of Hartley Avenue, Leeds
Amy Clancy, 24, of St Albans Avenue, Chiswick, west London
Melanie Evans, 25, of Elmfield Drive, Marple, Stockport, Greater Manchester
Brian Farelly, 32, of Vicarage Grove, London
Matthew Fawcett, 34, of Rockdove Avenue, Manchester
Grainne Gannon, 26, of Vicarage Grove, London
Robin Gillett, 23, of Granville Road, Manchester
Louise Hemmerman, 31, of Hartley Avenue, Leeds
Bryn Hoskins, 24, of Byfield, Isleworth, London
Kristina Jones, 22, of Hamilton Road, Manchester
Jasmin Karalis, 25, of Cadogan Terrace, London
Paul Morozzo, 42, of Chiserley Gardens, Hebden Bridge, West Yorkshire
Ellen Potts, 33, of Leighton Crescent, London
Oliver Rodker, 40, of Hamilton Road, Manchester
Bertie Russell, 24, of St Albans Avenue, Chiswick
Thomas Spencer, 23, of Hamilton Road, Manchester
Jonathan Stevenson, 27, of Cadogan Terrace, London
Alison Stratford, 26, of Princess May Road, north London
Christopher Ward, 38, of Annelsey Road, Newport Pagnell, Buckinghamshire
Elizabeth Whelan, 23, of Arlington Street, Glasgow
Felix Wight, 26, of Chepstow Villas, London

The five people who pleaded guilty at an earlier hearing are:
Theo Brown, 22, Glyn Road, London
Malcolm Carroll, 53, Oxford Gardens, Stafford
Clemmie James, 24, Princess May Road, London
Thomas Johnstone, 25, South Mossley Hill Road, Liverpool
Paul Mellett, 29, Tutton Hill, Colerne, Chippenham

The two people who have indicted they will plead guilty are:
Caroline Williams, 25, Princess May Road, London
Sam Martingell, 24, Whingate, Leeds.