s 1
The limits of hours prescribed in paragraphs 2, 3 and 4 of Article 2 may be exceeded and the interval prescribed in paragraph 5 reduced, but only so far as may be necessary to avoid serious interference with the ordinary working of the undertaking— (a) in case of accident, actual or threatened, or in case of urgent work to be done to machinery or plant, or in case of force majeure ; or (b) in order to make good the unforeseen absence of one or more members of a shift.