Paragraph 4 Period for completion of work

If the work is not completed within [five or such other period as specified] years from the coming into force of this Order or such extended time as the decision-maker may on the application of the undertaker allow, then on the expiration of that period or such extended time (as the case may be) the rights by this Order granted to the undertaker for making and maintaining the works shall cease except as to so much thereof as is then substantially commenced.