Following years of debate, the creation of the Court of Appeal (Criminal Division) in England and Wales signified official recognition that the criminal process may sometimes result in unsafe convictions. Central to the operation of the appellate system, is the ability of individuals who claim that their conviction is in error, to revisit and re-examine evidence gathered during the investigation, as well as that relied upon at their trial. High-profile miscarriages of justice have often only been remedied when there has been defence access to materials post-conviction (which had often not been disclosed pre-trial). While there has (rightly) been critical attention paid to pre-trial non-disclosure and the risks this poses to justice, such scrutiny has been lacking post-conviction. And yet, it is arguable that the rationale of preventing miscarriages of justice underpinning the duties of pre-conviction disclosure, subsists post-conviction. However, the Supreme Court judgment in R (Nunn) v Chief Constable of Suffolk Constabulary & Anor.  UKSC 37 has made it more difficult to gain disclosure post-conviction. This paper details a worrying picture of inconsistency among police and prosecution authorities, with confusion over what should be retained (and how), and whether disclosure post-conviction should be permitted. It concludes that without significant intervention and reform, miscarriages of justice will continue uncorrected and the appellate system will become inconsequential.