As a judge, Parker found himself presiding over trials in areas of the law he was unfamiliar with. He claimed that the first summing up which he gave in a criminal trial was the first he had ever heard. However, by getting down to the work, he eventually mastered the job and by 1954 was promoted to the Court of Appeal. The more measured style of the appellate courts suited Parker more than the cut and thrust of the King's Bench, and his ability to get to the important details of a case was assessed as good by those who appeared before him. He proved that he had reasonable political judgment in 1957 when heading a tribunal over a minor political scandal connected with the setting of interest rates.