The film will be an accompaniment to the four-part drama coming to ITV next year and will give exclusive access to campaigner Alan Bates.

Bates has rigorously campaigned for nearly 20 years to uncover and expose the scandal that has been described as the most widespread miscarriage of justice in the British legal history. 

Over 14 years, the Post Office accused hundreds of sub postmasters of theft, over 700 were given criminal convictions and many went to prison, ruining livelihoods and destroying reputations. 

The sub postmasters suffered from financial ruin and deterioration of their mental and physical health, resulting in at least one person tragically taking their own life.

The film will include the sub postmasters whose lives were turned upside down and have fought for justice ever since.

After Bates was terminated by the Post Office in 2003 when a shortfall was found in his accounts, he refused to accept it was due to his error and suspected the computer system Horizon was at fault. 

Bates brought together hundreds of other sub postmasters who had suffered a similar fate and took the Post Office to court and won.

However, his fight is not over as he continues to demand justice and compensation for the victims.