The Post Office Horizon Scandal has been called the widest miscarriage of justice in modern British history, with the number of former Sub Postmasters whose convictions have been overturned now over 60. Those who suffered prosecution or financial ruin due to errors on the Post Office's Horizon computer system want answers. How could this have happened? Who is responsible? Continuing the series that has helped expose the scandal since 2020, Nick Wallis draws on interviews, documents and the extraordinary revelations spilling out of the ongoing public inquiry. For the first time, the public is getting real insight into what was really going on inside the Post Office. In Episode 15, we hear how the Post Office ruined the life of Lee Castleton, a Sub Postmaster based in Bridlington who was taken to court over debts he says came from the Horizon computer system. New evidence reveals that the Post Office failed to investigate Lee's claims of computer errors in depth before taking him to court, and shows that evidence that may have cast doubt on Horizon was known about but not provided at the trial. Presenter: Nick Wallis Producer: Robert Nicholson Sound Design and Mixing: Arlie Adlington Executive Producer: Will Yates A Whistledown production for BBC Radio 4