13Where any expenses incurred by the Greater London Council in the discharge of their said functions are by virtue of paragraph 11 of this Schedule chargeable on part of a London borough, any payments made by the council of that borough for meeting precepts for defraying expenses incurred by some other body of persons in the discharge of the like functions with respect to another part of the borough shall be chargeable only on that other part of the borough or such part thereof as the council of that borough shall determine under section 23 of the Act of 1930 (whether as originally enacted or as applied by any other enactment).