In section 1 for the words from " on attaining the age of seventy years " to the end substitute the words " at the end of the completed year of service in which he attains the age of seventy ; but where the Lord Chancellor considers it desirable in the public interest to retain him in office after that time, the Lord Chancellor may from time to time authorise him to continue in office up to such age, not exceeding seventy-two, as the Lord Chancellor thinks fit ".