Where an appellant or applicant is in custody and has obtained leave or is entitled to be present at the hearing of his appeal or application, the Clerk of Justiciary shall notify the appellant or applicant, the Governor of the prison in which the appellant or applicant then is, and the Prison Commissioners for Scotland of the probable day on which the appeal or application will be heard. The Prison Commissioners for Scotland shall take steps to transfer the appellant or applicant to a prison convenient for his appearance before the High Court, at such reasonable time before the hearing as shall enable him to consult his legal adviser, if any.