He was appointed as a High Court judge on 3 October 1994, assigned to the Chancery Division, and received the customary knighthood.

He was promoted to the Court of Appeal on 15 January 2002 and, as is customary, became a member of the Privy Council.

[3] By Royal Warrant, all members of the Supreme Court, even if they do not hold a peerage, are entitled to the judicial courtesy title "Lord" for life.

Lord Carnwath is an honorary professor of law at University College London, an Honorary Fellow of Trinity College, Cambridge, and a visiting professor in practice at the Grantham Research Institute at the London School of Economics.

He is a former governor of the Royal Academy of Music (Hon FRAM) and former chairman of the Britten-Pears Foundation.