When a computer system installed by the Post Office malfunctioned, it led to the convictions of scores of subpostmasters for theft and false accounting. Lives were wrecked. After an ITV dramatisation brought new attention to the case, the Metropolitan police said they had commenced a criminal fraud investigation in relation to the Post Office. Today we re-run our episodes from 2021 on the scandal in full. Help support our independent journalism at theguardian.com/infocus