Policy choice, not perfection.

That is the clear message for local authorities from the Competition Appeal Tribunal’s recent judgment on the Cardiff Airport subsidy. In Bristol Airport v Welsh Ministers (7 April 2026), the Tribunal reaffirmed an important principle for public bodies: subsidy control is not about achieving the “right” answer, but about reaching a rational, well reasoned decision.

The Tribunal was clear that public authorities enjoy a real margin of discretion when applying the Subsidy Control Act 2022. Its role is not to re run economic assessments or revisit policy judgments, but to ask whether the authority’s reasoning was irrational in public law terms. Where a council or government body has identified a legitimate policy objective, considered relevant evidence and explained why it reached its conclusion, the Tribunal will not intervene simply because another view could have been taken.

That is particularly relevant for authorities navigating complex, high value interventions. The judgment recognises that decisions often turn on contested assumptions, imperfect data and difficult trade offs. Disagreement over the weight given to alternatives, counterfactuals or financial modelling will not, without more, cross the high threshold of irrationality. The law does not demand analytical perfection, it requires structured reasoning and defensible judgment.

For public authorities, the practical lessons are clear:

• Be explicit about the policy objectives a subsidy is intended to achieve
• Show that real alternatives have been considered and explained away
• Maintain a clear audit trail of advice, evidence and reasoning
• Sense check conclusions against the public law standard of rationality, rather than trying to eliminate every possible criticism

Taken together, the case offers welcome reassurance. Where public authorities take subsidy decisions carefully, transparently and for proper policy reasons, the UK subsidy control regime allows space for judgment  even in economically sensitive and politically exposed projects.