“In the latter case, the objection should be taken when the evidence is tendered and once the document has been admitted in evidence and marked as an exhibit, the objection that it should not have been admitted in evidence or that the mode adopted for proving the document is irregular cannot be allowed to be raised at any stage subsequent to the marking of the document as an exhibit. The latter proposition is a rule of fair play. The crucial test is whether an objection, if taken at the appropriate point of time, would have enabled the party tendering the evidence to cure the defect and resort to such mode of proof as would be regular. The omission to object becomes fatal because by his failure the party entitled to object allows the party tendering the evidence to act on an assumption that the opposite party is not serious about the mode of proof. On the other hand, a prompt objection does not prejudice the party tendering the evidence, for two reasons: firstly, it enables the court to apply its mind and pronounce its decision on the question of admissibility then and there; and secondly, in the event of finding of the court on the mode of proof sought to be adopted going against the party tendering the evidence, the opportunity of seeking indulgence of the court for permitting a regular mode or method of proof and thereby