As per case facts, ONGC and Tullow imported goods and seismic data tapes for petroleum exploration, claiming customs duty exemption under General Exemption No. 121. This exemption required an essentiality ... certificate from the Directorate General of Hydrocarbons at the time of importation. ONGC could not produce this certificate initially, which was later granted after importation, leading to a provisional clearance. The Tribunal dismissed ONGC's appeal for non-production but allowed Tullow's, remitting the matter. The question arose whether the production of an essentiality certificate, a condition precedent for customs duty exemption, could be accepted at a later stage, especially when the delay in its issuance was due to the administrative actions of a public authority rather than the importer. Finally, the Supreme Court held that if an importer is otherwise entitled to an exemption and the delay in producing a required certificate is caused by administrative inaction of a public functionary, the benefit of exemption should not be denied. Conditions that are not within the importer's control and depend on external public functionaries cannot be strictly enforced as conditions precedent to disable the benefit. The Court also clarified that public notices issued by a Custom House cannot override or alter the purport of statutory notifications. Accordingly, the Court dismissed Civil Appeal No. 5900 of 2004 and remitted ONGC's matter back to the Commissioner for reconsideration based on the essentiality certificate granted later.