18. Except in so far as in any particular case any privilege or immunity is waived by the Court, the judges and Registrar of the Court and any officer of the Court acting as Registrar shall enjoy, when engaged on the business of the Court and on journeys in connection with the exercise of their functions and, in the case of judges who are not citizens of the United Kingdom and Colonies, when residing in the United Kingdom for the purpose of holding themselves permanently at the disposal of the Court, the like privileges and immunities as in accordance with the 1961 Convention Articles are accorded to the head of a diplomatic mission.