A Lord of Appeal in Ordinary shall, if a Privy Councillor, be a member of the Judicial Committee of the Privy Council, and, subject to the due performance by a Lord of Appeal in Ordinary of his duties as to the hearing and determining of appeals in the House of Lords, it shall be his duty, being a Privy Councillor, to sit and act as a member of the Judicial Committee of the Privy Council.