Mel Broughton 48, of Semilong Road, Northampton, was jailed at Oxford Crown Court in February last year after he was found guilty of conspiracy to commit arson.
He appealed against his conviction earlier this year and, after taking more than a month to consider the verdict, Lord Justice Thomas returned to the Court of Appeal today to quash the conviction.
The judge, who heard the appeal with Mr Justice Kitchin and Sir Geoffrey Grigson, said an error in the way the trial judge summed up the evidence to the jury meant the conviction was "unsafe".
After an application by crown prosecutors, the judge ordered that Mr Broughton, who was not present in court, be retried on the allegation as soon as possible.
STEVE DISCOMBE IS A FATTY