In Hickey v. Illinois Central Railroad Company (1966), 35 Ill. 2d 427, 220 N.E.2d 415, the Illinois Supreme Court held that it was elementary that ordinary limitations statutes and principles of laches and estoppel do not apply to public bodies under usual circumstances, particularly when the governmental unit is the State. However, the Court went on to point out that the State may, in peculiar circumstances, be estopped when acting in a proprietary, as distinguished from its sovereign or governmental capacity. The Court went on to point out that it had always adhered to the rule that mere non-action of governmental officers is not sufficient to work an estoppel and that, before the doctrine can be invoked against the State, there must have been some positive acts by the officials which may have induced the action of the adverse party under circumstances where it would be inequitable to permit the Corporation to stultify itself by retracting what its officers had previously done. (35 Ill. 2d 427, 220 N.E.2d 415, 425-426.)