A FORMER Oxfordshire school pupil sentenced after a power station protest has had his conviction quashed.

Sam Martingell, who went to Henry Box School in Witney, was 24 in 2009 when he admitted obstructing the railway by stopping a train heading for Drax power station, North Yorkshire, the previous June.

A judge at Leeds Crown Court gave him a 12-month conditional discharge.

But yesterday all 29 of the protesters sentenced for their part in the stunt had their convictions quashed at the Court of Appeal.

The ruling follows concerns over the safety of the convictions, raised by the Director of Public Prosecutions in 2012 because the case had involved information obtained by undercover police officer Mark Kennedy.

The trial heard how the train was stopped by two men wearing orange jackets and hard hats.

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

The protest against fossil fuels linked to climate change lasted 16 hours.

Network Rail said the clean-up operation cost nearly £37,000.

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.