MUNICÍPIO DE MARIANA v BHP GROUP (UK) LIMITED

On an application to amend, the court must balance the applicant’s interest in determining the real dispute against fairness, proportionality, expedition and the court’s limited resources. A proposed amendment must be coherent, properly particularised, arguable and supported by a sufficient factual basis. A foreign-law allegation requires some legal expert evidence or other material where the pleaded interpretation is implausible on the documents. The court should avoid a mini-trial, but may refuse an amendment with no real prospect of success. Pleadings based on estoppel or abuse of process must identify the relevant elements and connect them to the facts. Security for costs should be assessed by applying the threshold test and then asking whether an order is just in all the circumstances; where the future scope and costs of a trial remain uncertain, the application may appropriately be adjourned.

The claims arise from the collapse of the Fundão Dam in Brazil. The claimants sought permission to make extensive amendments concerning environmental and socio-economic consequences, Brazilian compensation arrangements, recognised affected areas, estoppel and abuse of process. They also sought directions for a proposed Second Stage trial, disclosure concerning Brazilian compensation agreements, and continuation of litigation-friend appointments. The defendants sought security for costs, funding information and costs management.

The court permitted most amendments, refused amendments concerning alleged binding recognition of affected areas, and gave directions for the next stage of the litigation. The central issues included whether the opposed amendments were coherent and had a real prospect of success, and whether security for costs should be ordered before the scope and costs of the Second Stage trial were sufficiently clear.

1. Amendments. Applying CPR 17.1, CPR 17.3 and the overriding objective in CPR 1.1, the court balanced prejudice to the applicants against prejudice to the defendants, other litigants and the administration of justice. The proposed amendments had to be arguable, coherent, properly particularised and supported by evidence. The court should avoid a mini-trial, but could refuse an amendment with no real prospect of success, applying Kawasaki Kisen Kaisha Ltd v James Kemball Ltd [2021] EWCA Civ 33 and Okpabi v Royal Dutch Shell Plc [2021] UKSC 3.
2. Permission was granted for the unopposed amendments and for paragraphs 257B–257F and 257H, which gave an overview of the Reparations Agreement and advanced interpretations capable of being answered in the defence. Permission was refused for paragraphs 257G and 257I and Appendix VI. The pleaded inference that the agreement established binding recognition of affected areas was incoherent and unsupported. Clause 146 provided a complete answer to the alleged preclusion, and no legal expert evidence or other material supported the proposed contrary Brazilian-law interpretation.
3. The proposed Brazilian-law case also lacked identification of the applicable principles, explanation of their application, and supporting expert evidence. The alleged estoppel was unparticularised. The abuse-of-process case had no real prospect of success: the Brazilian proceedings had been stayed, discontinued or settled without adjudication of the relevant issues, and the defendants had not been parties. The proposed recognition of areas was also too general to assist in deciding whether individual claimants had suffered recoverable loss.
4. Security for costs. Under CPR 25.26 and CPR 25.27, the threshold condition was satisfied, but it was not yet just to order security. The scope, evidence, timetable and costs of the Second Stage trial remained uncertain; the outcome of the First Stage trial was awaited; and costs management was pending. The application was adjourned to the December 2025 CMC. The claimants were ordered to disclose funders’ identities and contact details by 25 July 2025.
5. Directions were given for pleadings, selection of potential lead claimants, questionnaires, identification of issues and preparation for the Second Stage trial. The costs of the amendments were costs in the case, except that the claimants were to bear the costs of amendments to Appendix III.