Mass tort claims in England: 5 takeaways from Mariana v BHP for businesses operating overseas

On 14 November 2025 the English High Court handed down judgment in a high profile mass tort claim arising from a 2015 dam failure in Brazil.

In this note, we consider the implications of the judgment in Municipio de Mariana v BHP Group [2025] EWHC 3001 TCC. The full judgment and summary are available here.

Background to the claim and procedural history

In 2015 the Fundão dam in Brazil collapsed. It is considered the worst environmental disaster in the country's history. As a result, a number of class actions and thousands of individual claims were brought in Brazil.

In the midst of these actions, 200,000 Brazilian claimants brought a group claim in the English courts, the largest ever mass tort claim in UK legal history. The dam was owned and operated by Samarco Mineração S.A. (Samarco), a Brazilian mining company. It was jointly owned under a joint venture agreement by BHP Brasil and another mining company (Vale S.A.). The claims in the English courts were brought against BHP Group Limited (BHP Australia), as the ultimate parent company of BHP Brasil, and BHP Group (UK) Limited, which operated with BHP Australia as a single economic entity at the time of the collapse. The English court had jurisdiction as BHP was listed on the London Stock Exchange at the time of the disaster.

The claim was struck out by the High Court in 2020. This was due to the practical difficulties that would arise in hearing the claim, particularly due to its size and the fact that the events leading to the claim took place exclusively in Brazil. Mr Justice Turner also referred to the “unremitting” compensation schemes and proceedings in Brazil that would be concurrent with the English proceedings, suggesting that this would lead to "utter chaos".

Mr Justice Turner initially refused permission to appeal. The Court of Appeal subsequently did the same. Permission to appeal was then reopened on an exceptional basis. The decision to strike out the claim was overturned in July 2022. The claim proceeded and on 14 November 2025, the High Court handed down its long-awaited judgment following the First Stage Trial, which took place between October 2024 and March 2025.

BHP and Vale separately reached an agreement in 2024 on sharing responsibility between them. Vale was not a party to the proceedings.

Summary of the decision

The decision was largely in favour of the claimants, of which there are now over 600,000. These comprise a mix of individuals, businesses, faith-based institutions, municipalities, utility companies and indigenous and other minority community members. The First Stage Trial focused on liability.

Mrs Justice O'Farrell drew the following conclusions:

i. Although BHP was not the direct legal owner of the dam, by their control and operation of Samarco, BHP were directly or indirectly responsible for the polluting activity. BHP were therefore strictly liable as "polluters" under Brazilian law.

ii. BHP were also liable for fault-based liability, as they knew or should have known that certain technical attributes of the dam would not withstand an increase in its height, which ultimately caused its collapse.

iii. BHP were not found to be in breach of their duties and responsibilities as a controlling shareholder in Samarco, by reason of abuse of power.

iv. The claims were not precluded by limitation periods.

v. No constitutional impediment existed for municipalities to bring proceedings in the English courts.

vi. A number of the claimants had received compensation and entered into settlement agreements. The court considered the principles for assessing the validity, and interpretation of, these settlements at a later stage of the litigation.

Key takeaways

1. The English courts can and will consider mass tort claims

The claim was initially struck out as it was found to be "irredeemably unmanageable". As the claim ultimately went ahead, the ability of the English courts to manage such mass tort claims was put to the test. The judgment illustrates the English courts' ability to handle a very large, and technically complex case based on the law of a different jurisdiction. Although the litigation was heard in England, Brazilian law governed the substantive issues, as the law of the country where the damage occurred.

From a case management perspective, the court's division of the trial into the First Stage Trial, which dealt with liability, and Second Stage Trial, which will deal with damages, made the case easier to manage.

In terms of the legal difficulties in dealing with the law of another jurisdiction, Mrs Justice O'Farrell relied on Brazilian law experts across a number of disciplines. At paragraph 234 of the judgment, Mrs Justice O'Farrell noted that where the parties relied on foreign law, the law must be 'pleaded and proved as a fact', as is standard practice.

The judgment provides a template for how the English court may approach similar claims. It is likely to encourage litigation in the jurisdiction against businesses arising from overseas harm.

2. The court will scrutinise parental control and responsibility for subsidiaries

The claimants alleged that BHP had strict liability for the dam collapse as a "polluter" under Articles 3(IV) and 14, paragraph 1 of Brazil's Environmental Law. The assessment of this question required a multifactorial analysis, including BHP's control over the polluting activity, degree of involvement in the activity, financing of the activity and economic benefit from the activity.

In particular, Mrs Justice O'Farrell considered factual questions of whether, and to what extent, BHP had assumed control over Samarco.

The question of parental control has been considered by the English courts in other ESG-focused group actions such as Vedanta Resources PLC and another v Lungowe and others [2019] UKSC 20 and Okpabi v Royal Dutch Shell Plc [2021] UKSC 3. In these cases, the court demonstrated its openness to holding parent companies liable for subsidiaries' wrongdoing. In each case the court emphasised that whether a parental duty of care arises is a "pure question of fact".

The analysis performed by Mrs Justice O'Farrell illustrates the factors which are likely to be relevant to an assessment of parent company control, irrespective of the governing law.

Mrs Justice O'Farrell referred to Samarco's corporate structure, in which BHP (and Vale) determined the make-up of the board, and BHP's responsibilities over Samarco's activities and operations such as long-term strategy, and financial and technical audits. She also referred to the funding of major Samarco projects by BHP.

Mrs Justice O'Farrell noted that BHP was involved in Samarco "at every level" from "strategic decisions and dividend shares to detailed operational matters at Samarco."

The litigation involved an extensive disclosure exercise. Material which Mrs Justice O'Farrell referred to in her judgment included "monthly spreadsheets that were sent by the [BHP] Iron Ore Brazil Team to Samarco, identifying deadlines for deliverables on topics such as costs, cash flow, planning, production, projects, risk and critical incidents" and "financial and technical audits of Samarco’s operations, the findings of which were reported to, and considered by, BHP at the [Group Management Committee – BHP's senior management team] and subsequently monitored."

Mrs Justice O'Farrell cited these documents as evidence of BHP's control and operation of Samarco. She therefore found that BHP bore strict liability for the harm caused.

One of the attractions of litigation in England for claimants is disclosure. It permits claimants to seek, and receive, extensive materials illustrating how companies operate, and manage and assess risk. The judgment serves as a reminder that the English court has the tools, and the appetite, to sift through corporate documents to determine how parents and subsidiaries operate in fact.

3. The question of fault: negligence liability for multinational companies

BHP was also found to be negligent under Brazilian Law, specifically Article 186 of the Civil Code. This imposes liability on anyone who by act or omission, negligence or imprudence violates a right and causes damage to another.

In this case, the standard of conduct by which BHP was assessed was on an objective basis. This was by reference to the "conduct of an average mining and tailings dam business owner", actively involved in the "planning, operation, risk assessment and control of the dam". This formulation of the standard of care echoes the approach under English law.

Mrs Justice O'Farrell concluded that by August 2014 (15 months before the collapse) BHP knew, or should have known, that the physical condition of the dam was perilous. She identified contemporaneous reports which identified mitigation actions in respect of a potential failure of the dam. The action items contained in these reports remained outstanding. Mrs Justice O'Farrell concluded that the collapse of the dam was foreseeable, and avertable. BHP was therefore liable under Article 186 of the Civil Code.

The judgment illustrates the risks for companies operating in high risk sectors if they do not act on prudent engineering advice. The court will assess what a company knew and when it knew it. Such assessment will inform whether the company fell short of the standard imposed on it by the law.

4. The other defences: limitation and settlement agreements

Limitation

One of BHP's defences was that certain claims were extinguished by limitation (known as "prescription" under Article 189 of the Brazilian Civil Code). There was a debate as to whether the claim forms issued in England contained sufficient detail to stop time running for this purpose. Mrs Justice O’Farrell determined that the claim forms in this case included sufficient detail to "stop the clock" running.

Limitation periods can vary by jurisdiction; under Brazilian law, the limitation period for civil redress is 3 years, while under English law, this is generally 6 years. The Brazilian Consumer Defence Code contains a specific 5 year limitation period. Parties to litigation involving claims under governing laws other than that of England should consider carefully the applicable deadlines. Do not assume that an English limitation period will apply.

Settlement agreements

The validity, and interpretation, of the settlement agreements in Brazil prior to the commencement of proceedings in the English courts was in issue. Mrs Justice O’Farrell did not discuss whether specific settlement agreements would withstand challenge, although she outlined the relevant Brazilian legal principles.

In response to the judgment, in BHP's statement of 14 November 2025, they stated that the findings on the settlements should reduce the size and value of the claims in the English proceedings.

It is important to consider the extent to which settlement agreements agreed in a foreign jurisdiction will "hold" in English proceedings, or can be unwound. Claimants who pursue claims in England may well seek to evade or limit the effect of existing settlement agreements.

5: The end of the beginning? More litigation to come

The Second Stage Trial will consider the damages owed to the claimants. Given the size of the case, this will likely be an extremely complex analysis.

In its statement of 14 November 2025, in response to the judgment, BHP stated that they intend to appeal the decision. They also raised the potential for a Third Stage Trial, where each remaining claimant would need to prove their individual damages. BHP's expectation is that all trials will not be complete before 2028 or 2029.

The decision of the First Stage Trial is therefore unlikely to be the end of the story. Absent a settlement of the English claims, the litigation will continue for years to come.

Conclusion

This landmark case has set a precedent that tort claims of this size, even those with a basis in foreign law, can be brought effectively in the English courts.

Alongside cases such as Vedanta and Shell, the judgment in Mariana v BHP emphasises that a parent company can be found liable for the actions of its subsidiary. This should prompt careful consideration of parental involvement throughout a group structure, whether abroad or at home. The English court will look carefully at how companies operate in practice, and the documentary evidence for this. Companies will find it harder to argue that they do not owe parental responsibility for the actions of their subsidiaries if the facts point to extensive control and involvement.

Other author: Anjali Vaz, Associate