s 13 Authentication of seal
All deeds, documents and other instruments requiring the seal of the Board shall be sealed with the common seal of the Board in the presence of the Chairman and the chief executive officer, or either the Chairman or the chief executive officer and one other member of the Board or any two other members of the Board, and any deed, document or instrument purporting to be sealed with the common seal of the Board and so authenticated shall until the contrary is proved, be deemed to have been validly executed: Provided that where the Chairman is also the chief executive officer the common seal of the Board shall be sealed in the presence of the Chairman and one other member of the Board or any two other members of the Board.