Where a building shall have been certified under the hand of one of Her Majesty’s Principal Secretaries of State, to the bishop of the diocese within which such building is locally situate, as used or intended to be used by Her Majesty’s military forces as an unconsecrated chapel for the purpose of divine worship according to the rites and ceremonies of the said . . . F1 Church, it shall be lawful for one of Her Majesty’s Principal Secretaries of State from time to time to appoint any army chaplain to perform all the functions of an army chaplain therein; and if at any time such building shall cease to be used for the purpose aforesaid, it shall be lawful for one of Her Majesty’s Principal Secretaries of State to certify such fact to the said bishop, and thereupon the provisions of this Act shall no longer apply to such building.