Regulation 11 provided: "The Board may amend the terms and conditions of supply from time to time, provided that any amendment having the effect of enhancement of charges payable by the consumer shall come into force from such date as notified in the Gazette provided that there shall be at least 30 days between the date of publication and coming into force." In exercise of the power so reserved to it, the Board issued a notification dated 16.7.1968 (Exhibit P/2) which provided: "In accordance with the provisions contained in clause 11 of the Kerala State Electricity Board (General Tariffs) Regulations issued in Kerala Gazette No. 47 dated 29.11.1966, it is hereby notified that the rates for the supply of 4200 K.W. of power at 66 K.V. to messrs F.A.C.T. availed by them as per the agreement dated 21.10.1948 executed with the erstwhile Travancore Government, is hereby revised to Rs. 200 per K.V.A. per year.