The Dekagram: 26th January 2026

This week we welcome Imogen Todd to the Dekagram team. Imogen, who was taken on as a tenant in October, brings news of an important Supreme Court decision on ex turpi causa (the illegality defence), in which no fewer than three members of chambers were involved (Andrew Warnock KC, Jack Harding, and  Gurion Taussig). Sarah Prager KC also has news, in her case an update on the juggernaut Brazilian Dam litigation.

Ex turpi causa: Lewis-Ranwell v G4S Health Services (UK) Limited & Others [2026] UKSC 2

In February 2019, Mr Lewis-Ranwell unlawfully killed three men during a schizophrenic episode. As a criminal Defendant, Mr Lewis-Ranwell was found not guilty by reason of insanity under the Trial of Lunatics Act 1883. The court imposed Hospital and Detention orders and Mr Lewis-Ranwell was detained in a secure hospital.

Mr Lewis-Ranwell brought civil claims against various public authorities, arguing that had the public authorities not acted negligently, the killings would not have happened. He therefore sought damages for personal injury, loss of liberty, reputation, and pecuniary losses that resulted from the killings and his ultimate detention.

Before considering the substantive issue of negligence, the courts needed to address the preliminary issue of whether the claim was barred by the illegality defence (ex turpi causa). The illegality defence is a public policy that prevents a claimant from recovering damages or enforcing a claim if that claim is founded upon the claimant’s own immoral or illegal act. The difficulty in this case is that the claimant was found not guilty of murder by reason of insanity and so is deemed not criminally responsible for the killings.

Both the High Court and the Court of Appeal (apart from Lady Justice Andrews) considered that the illegality defence applies only where the claimant is criminally responsible for their acts. This idea was also teased in preceding diminished responsibility cases.

On 21 January 2026, the Supreme Court confirmed the test to be applied in illegality defence cases, and in doing so, that neither criminality nor criminal responsibility are required for the illegality defence to apply.

The test is as follows:

First, the threshold question must be addressed: the conduct must be sufficiently serious and closely connected to the claim.

Second, the Patel v Mirza [2016] UKSC 42 [120] assessment:

“The essential rationale of the illegality doctrine is that it would be contrary to the public interest to enforce a claim if to do so would be harmful to the integrity of the legal system (or, possibly, certain aspects of public morality, the boundaries of which have never been made entirely clear and which do not arise for consideration in this case). In assessing whether the public interest would be harmed in that way, it is necessary

(a) to consider the underlying purpose of the prohibition which has been transgressed and whether that purpose will be enhanced by denial of the claim,

(b) to consider any other relevant public policy on which the denial of the claim may have an impact and

(c) to consider whether denial of the claim would be a proportionate response to the illegality, bearing in mind that punishment is a matter for the criminal courts.”

No part of the test required the underlying conduct be criminal or that the prospective claimant be criminally responsible for the wrong. Lord Hodge and Lord Lloyd-Jones founded these conclusions on the core principle: you shall not kill. The distinction between diminished responsibility and insanity in criminal law could not govern the defence’s scope in civil law. The claimant’s conduct in killing three men without lawful justification remained unlawful and engaged the illegality defence in these civil proceedings.

The court accepted that it is in the public interest for the court to adjudicate civil wrongs but considered that the civil wrong claimed in this instance is better suited to an alternative forum, such as an inquest or inquiry.

The judgment is a welcome clarification on the scope of the illegality defence and that the test did not need to mirror criminal law to be compatible with it.

About the Author

Imogen Todd was called in 2020. Having completed pupillage at Deka Chambers, including a period under the tutelage of Dominique Smith, she was taken on in October 2025. She now undertakes a broad civil practice, with a strong track record in personal injury, travel claims, inquests, stage 3 hearings, infant approval hearings and credit hire litigation.

Interest on Costs Not Yet Paid: Município De Mariana v BHP Group (UK) Ltd & Another [2026] EWHC 73 (TCC)

Regular readers will already be all too familiar with the facts of the Brazilian dam litigation, but to recap: in late 2015, the Fundão dam in south-eastern Brazil collapsed. The collapse of the dam had catastrophic consequences, releasing vast quantities of iron ore mine tailings into the Doce River, which damaged, destroyed or contaminated everything in its path. Villages were obliterated, individuals died, and thousands suffered loss. 

On 14^th November 2025 the High Court handed down judgment. It found:

1. The defendants are strictly liable as “polluters” in respect of damage caused by the collapse pursuant to Articles 3(IV) and 14, paragraph 1 of the Environmental Law.
2. The alternative strict liability claim pursuant to Article 927, sole paragraph of the Civil Code does not arise.
3. The defendants are liable based on fault in respect of damage caused by the collapse, pursuant to Article 186 of the Civil Code.
4. The defendants are not liable in respect of damage caused by the collapse pursuant to Articles 116 and/or 117 of the Corporate Law.
5. The claim forms issued in the proceedings before the court contained sufficient information, as required by Brazilian Law, to stop time running for the purpose of limitation/prescription.
6. Pursuant to Article 200 of the Civil Code, the criminal investigation and proceedings that were commenced in Brazil in November 2015 postponed the start of the prescription period until at least 2024.
7. The ADIC CPA filed against Samarco on 17 November 2015 interrupted prescription in respect of all claims arising out of the collapse but such interruption terminated on 24 September 2018.
8. The ambit of the thesis in Theme 999 is limited to public environmental claims, that is, claims for relief regarding the restoration of damage to the environment. It does not extend to claims for individual or collective compensation arising out of damage to the environment, which remain subject to the general rules of prescription.
9. The prescription period for the claims is five years pursuant to Article 27 of the Consumer Defence Code.
10. The claims by the Municipalities and Utilities are subject to a five-year prescription period pursuant to the 1932 Decree.
11. The Term of Commitment document entered into by Samarco, BHP Brasil and Vale on 26 October 2018 is of no assistance.
12. The general rule is that the prescription period starts from the moment at which the injury to the right occurs but subject to the characterisation of the injury; a distinction must be drawn between a single harmful event, periodic violations of right, and continuous violation.
13. Certain claimants may be entitled to extended prescription periods, by reference to (a) filing of protests in Brazil, (b) lack of capacity and/or (c) their date of knowledge. It would be a matter for the court, in each case, to determine these issues on the facts.
14. The settlement agreements are regulated by the general principles of contractual interpretation contained in the Civil Code. The Consumer Defence Code does not apply to the settlement agreements because there is no underlying consumer relationship between the parties and the settlement agreements are not consumer contracts.
15. The court has determined the issues of construction and principle arising in respect of the sample settlement agreements.
16. There is no constitutional impediment by way of incapacity for the Municipalities to bring proceedings in this jurisdiction and they have standing in these proceedings.

On 19^th January Mrs Justice O’Farrell DBE heard the parties on the issue of whether the claimants were entitled to claim interest on the costs awarded to them, notwithstanding that the claims are funded by way of a conditional fee agreement, and the claimants themselves were therefore not yet out of pocket as a result of the litigation. To put the question into perspective, costs were said to be £189 million, and a payment on account was sought in the sum of £113.5 million.

At paragraphs [13] to [15] the court provided a succinct summary of the position as regards the costs of a split trial:

13. Where there is a split trial, the court is entitled to exercise its discretion to make an immediate order for the payment of costs in respect of the liability trial but may defer the issue of those costs until the final outcome of the litigation, especially if it is unclear whether the successful party will recover more than nominal damages: Weill v Mean Fiddler Holdings Ltd [2003] EWCA Civ 1058, at [31] to [34].

14. However, as a general rule, costs should follow the issue, regardless of when the issue is determined, particularly in complex disputes, to encourage the parties to adopt a proportionate approach to the litigation by focussing on the significant and meritorious points: Langer v McKeown [2021] EWCA Civ 1792 at [36]-[38]; Illiquidx Ltd v Altana Wealth Ltd [2025] EWHC 1566 (Ch) per Rajah J at [8].

15. The fact that a party has not won on every issue is not, of itself, a reason for depriving that party of part of its costs. In the absence of unreasonable conduct in pursuing or resisting an issue, the general rule is that the successful party should have their costs and should only suffer a reduction to the extent that the costs were increased by the taking of the issue on which they failed: Sharp v Blank [2020] EWHC 1870 (Ch) per Sir Alistair Norris at [7](a)-(g).

O’Farrell J concluded that she should make a costs order in favour of the claimants, who had won on the key liability issues, but reduced this by 10% to reflect the fact that the claimants had not won on every issue. She allowed a payment on account of costs in the sum of a mere £43 million, amounting to only 60% of the costs she thought might be properly recoverable in respect of the trial itself, rather than other costs incurred in the litigation as a whole (bearing in mind the 10% reduction).

The claimants sought interest at the commercial rate of 1% above base rate on the totality of their costs as from 1 August 2023, the date at which half of the fees were incurred. The defendants’ position was that the claimants were not entitled to any interest on pre-judgment costs because they have not paid any legal fees or disbursements up front and have not explained how they are out of pocket. At paragraph [51] of the judgment O’Farrell J set out her reasons for acceding to the claimants’ submissions:

In this case, the claimants have not been required to fund the litigation directly and have made no payments in respect of costs. Pogust Goodhead have obtained funding for the litigation and the claimants do not have to pay any costs unless and until any damages are awarded. However, in that eventuality, the claimants will be liable to pay success fees to their legal representatives reflecting the costs of funding the litigation, thereby reducing any damages received. It is a liability for costs, albeit a contingent liability at this stage. As a matter of principle, the claimants should be entitled to compensation in respect of the funding expenses for which they will be indebted out of any damages. The fact that their solicitors and/or funders have accepted the risk that the costs and funding expenses will only be recouped from any damages does not detract from that position.

With respect, this line of reasoning does not appear to engage with the defendant’s argument that the claimants were not and would not be liable to pay interest on costs they had not incurred; the payment of a success fee is a different concept, and not a matter for the defendant, it is suggested. It will be interesting to see whether the defendant appeals this aspect of the contingent orders, given that it has indicated an intention to appeal the substantive orders on the issue of liability. For the time being, however, the decision stands, albeit as an example of the exercise of the court’s discretion.

About the Author

Called to the Bar in 1997, Sarah Prager KC has been listed in the legal directories in travel law for many years, and, more recently, listed in aviation as well. Together with Matthew Chapman KC, Jack Harding, Dominique Smith, Tom Yarrow and Henk Soede, she co-writes the leading legal textbook in the area, and has been involved in most of the leading cases in the field in the last few decades. She undertakes purely domestic high value personal injury work as well as cross border work and has a wealth of experience of difficult and sensitive cases, including serious sexual assault and cases involving children.