Competition – Practice. The Chancery Division gave guidance on the proper procedure to be followed for the hearing of applications to vary or discharge a warrant granted to the Competition and Markets Authority (CMA), under s 28, the Competition Act 1998, to enter premises for the purpose of searching and taking copies of documents relating to an investigation into suspected anti-competitive behaviour. The CMA had successfully applied to set aside an order in favour of the defendant (Concordia), varying the warrant. However, that decision had been based on (possibly sensitive) information, which had not been disclosed to Concordia. The court held that the application to vary or discharge a warrant issued under s 28 of CA 1998 should be by way of a rehearing, and that the process of asserting and adjudicating upon claims of public interest immunity should be incorporated into the ex parte application by the CMA for the s 28 warrant. Accordingly, it held that the CMA should have identified, at the outset, what material it contended should have been redacted on public interest immunity grounds, and that Concordia's application to vary or partially revoke the warrant had had to be determined on the basis of such material as was not protected by public interest immunity.