ARCHIVED–this archived case hub reflects the position at the date of the judgment of 11 December 2020; it is no longer maintained. See further, timeline, commentary and related cases. Case facts Outline Appeal against the Court of Appeal’s judgment of 16 April 2019 which allowed Walter Merricks’s appeal against the Competition Appeal Tribunal’s judgment of 21 July 2017 refusing to grant a Collective Proceedings Order. Latest development On 11 December 2020, the Supreme Court issued its judgment in which it upheld the Court of Appeal’s judgment and remitted to Competition Appeal Tribunal for reconsideration. In particular, the Supreme Court agreed with the Court of Appeal that the CAT made numerous errors of law in refusing to certify Mr Merricks’ mass consumer collective action. Parties Appellants:Mastercard Incorporated, Mastercard International Incorporated and Mastercard Europe S.P.R.L (together, Mastercard). Mastercard is the international payment organisation responsible for managing and coordinating the Mastercard and Maestro card payment systems which includes, amongst other things, establishing the rules for the system and providing participating