Here (Sweetman v Shell), the Supreme Court held that Part 2 of the Environmental (Miscellaneous Provisions) Act 2011 (Costs of Certain Proceedings to be Borne by Each Party in Certain Circumstances) (link) does not act retrospectively. Charleton J stated: This is because the award of costs is not essentially procedural. An expectation as to the recovery of costs affects both the decision to commence a case and the necessary and legitimate prediction that it would be funded if successfully prosecuted or successfully defended by the party required to answer a legal action. Laffoy J and Dunne J concurred.