7E+WIf in the course of the execution of undertakers’ works under paragraph 5 above—
(a)apparatus of better type, of greater dimensions or of greater capacity is placed in substitution for existing apparatus of worse type, of smaller dimensions or of smaller capacity, or
(b)apparatus (whether existing apparatus or apparatus substituted for existing apparatus) is placed at a depth greater than the depth at which the existing apparatus was,
and the placing of apparatus of that type, dimensions or capacity or the placing of apparatus at that depth, as the case may be, is not agreed by the authority concerned, or, in default of agreement, is not determined by arbitration to be necessary, then, if it involves cost in the execution of the undertakers’ works exceeding that which would have been involved if the apparatus placed had been of the existing type, dimensions or capacity, or at the existing depth, as the case may be, the amount which apart from this paragraph would be payable to the undertakers by virtue of paragraph 6 above shall be reduced by the amount of that excess.