3.—(1) The undertaker must, before commencing construction of any relevant work, supply to Network Rail proper and sufficient plans of that work for the reasonable approval of the engineer and must not commence construction of any relevant work until plans of that work have been approved in writing by the engineer or settled by arbitration.
(2) The approval of the engineer under sub-paragraph (1) is not to be unreasonably withheld or delayed, and if by the end of the period of 56 days beginning with the date on which such plans have been supplied to Network Rail the engineer has not indicated disapproval of those plans and the grounds of his disapproval, the engineer will be deemed to have approved the plans as submitted.