In a legality review, despite the absence of a fixed time limit (unlike PAJA's 180-day bar), the application must be brought without undue delay. Whether delay is unreasonable involves a factual, multi-factor and context-sensitive inquiry considering: the length of delay, reasons for it, prejudice to parties, fullness of explanation, and prospects of success. Where an organ of state has knowledge of alleged irregularities but continues to act on the agreements, demands performance, and allows substantial expenditure before launching review proceedings, the delay is unreasonable and cannot be condoned without undermining reliance, accountability and rationality. A change in political administration of an organ of state does not justify delay as the entity remains a single juristic person. Not every flaw in public procurement is fatal; immaterial irregularities do not invalidate contracts. When determining whether to set aside administrative decisions under section 172 of the Constitution, courts must weigh the consequences of setting aside against not setting aside, particularly where substantial performance has occurred and innocent third parties will be prejudiced. Public procurement contracts should not be invalidated for immaterial or inconsequential irregularities.