shall hold office in accordance with the terms of his appointment, and

may resign by notice in writing to the Secretary of State.

that he has without reasonable excuse failed to carry out his functions for a continuous period of three months beginning not earlier than six months before the day of dismissal,

that he has been convicted of a criminal offence,

that a bankruptcy order has been made against him, or his estate has been sequestrated, or he has made a composition or arrangement with, or granted a trust deed for, his creditors, or

that he is unable or unfit to carry out his functions.