What is the rule of promissory estoppel?

The doctrine was applied in one case where the SC held that the CB may not thereafter renege on its representation and liquidate the bank after majority stockholders of the bank complied with the conditions and parted with value to the profit of CB, which thus acquired additional security for its own advances, to the detriment of the bank’s stockholders, depositors and other creditors. (Ramos v. Central Bank of the Philippines, G.R. No. L- 29352, Oct. 4, 1971)