He was elected to the Bar Council in 1957, was treasurer in 1964, vice-chairman in 1966, and chairman in 1968. He was appointed Recorder of Swindon in 1962, and became an Appellate Judge of Jersey and Guernsey in 1967, serving in both offices until he was appointed a High Court Judge of the Queen's Bench in 1971. He became a judge of the Commercial Court in 1973, and was promoted to become a Lord Justice of Appeal and was appointed to the Privy Council in 1980. Three years later, in 1983, he became an Honorary Fellow of the University of Cambridge.
In 1986, he was appointed Lord of Appeal in Ordinary, earning the right to sit as Baron Ackner, of Sutton in the County of West Sussex in the House of Lords. He joined in the majority in the House of Lords in 1987 in the 3:2 judgment imposing an injunction to prevent The Guardian, The Observer and The Sunday Times newspapers publishing extracts from Peter Wright's book, Spycatcher, saying that failing to impose an injunction would be a "charter for traitors". He also joined in decisions banning broadcasts by the IRA and Sinn Féin, and ruled in the R. v. R. case that a man could be convicted of the rape of his wife (overturning a century of judicial precedent).
Retirement
He retired as a Law lord in 1992 but continued to attend the Lords as a crossbencher. He remained active in Bar politics, supporting the traditional division of the legal profession in the UK and opposing the extension of rights of audience to solicitors.