[1] The respondents ("the Board") had contracted to supply electricity to the appellants. By mistake, it had considerably undercharged the appellants to the amount of $84,624.01 and successfully claimed that amount from them. The learned trial judge held that the Board was not estopped from claiming that amount although the appellants had utilised the accounts rendered by the Board forthe purpose of costing their products. To have admitted the estoppel, so the learned judge held, would have had the effect of nullifying the statutory provisions of the Electricity Act, 1949 (Revised - 1973).