21.—(1) Notwithstanding the temporary stopping up or diversion of any highway under the powers of article 10 (temporary stopping up of streets) , the undertaker shall be at liberty at all times to construct and do all such works and things in, upon or under any such highway as may be reasonably necessary to enable it to maintain, renew, protect or use any sewer which at the time of the stopping up or diversion was in that highway.
(2) Where, in consequence of this Order, any part of any street, bridleway or footpath in which any sewer is situated ceases to be part of the street, bridleway or footpath, the undertaker may exercise the same rights of access to such sewer as it enjoyed immediately before the coming into force of this Order, but nothing in this paragraph shall affect any right of the Council or of the undertaker to require alteration of such sewer under this Part of this Schedule.