Anti-anti-suit injunctions in family proceedings: lessons from Potanina v Potanin

The long-running litigation between Natalia Potanina and Vladimir Potanin has broken new ground once more. In a judgment delivered on 12 August 2026, Mr Justice MacDonald dealt with what appears to be the first application in family proceedings for an anti-anti-suit injunction. The wife also sought anti-enforcement and anti-reliance orders.

The case is notable not only for its extraordinary facts and the scale of the wife’s US$5 billion claim, but for the clear reminder that establishing English jurisdiction—or even demonstrating that England is the natural forum—does not by itself justify exceptional equitable relief.

From Part III claim to competing injunctions

The wife issued proceedings in 2018 under Part III of the Matrimonial and Family Proceedings Act 1984, seeking financial relief after the parties’ Russian divorce. Following litigation that reached the Supreme Court, the Court of Appeal granted her unconditional leave to proceed in September 2025. Her needs and sharing claims are listed for a final hearing in November 2026.The husband has been a designated person under the Russia (Sanctions) (EU Exit) Regulations 2019 since June 2022. In February 2026, once his final challenge to the grant of leave had failed, he applied to the Moscow Arbitrazh Court under articles 248.1 and 248.2 of the Russian Commercial (Arbitrazh) Procedure Code. 

Those provisions give Russian commercial courts exclusive jurisdiction in certain disputes involving sanctioned persons and allow them to restrain foreign proceedings.

On 18 May 2026 the Russian court prohibited the wife from continuing her English claim, required her to terminate it within 15 days, and barred her from taking steps to neutralise the Russian order. Non-compliance carried the risk of a penalty, or astreinte, that could reach the value of her English claim.

On 2 June the wife obtained without-notice anti-anti-suit, anti-enforcement and anti-reliance injunctions from Lieven J. These restrained the husband from pursuing or enforcing the Russian order, seeking penal relief, or relying in Russia on the wife’s continuation of the English proceedings. MacDonald J had to decide at the return hearing whether that protection should continue.

Substance over form

The wife characterised the orders as interim measures that would last only until the Part III proceedings concluded. The court took a different view and treated them as effectively final. The Russian order had already been made. The wife had continued the English proceedings in breach of it and would face potential penalties if the English protection were lifted. It was hard to see how the relief could sensibly be revisited once the Part III case was over.

That conclusion raised the threshold. The wife had to establish her entitlement to the high standard required for a final injunction, rather than the familiar American Cyanamid test. An anti-enforcement injunction is in any event exceptional, and the mandatory reporting provision demanded a high degree of assurance.

Practitioners should therefore look past the proposed duration and wording of an order. Where the practical consequences cannot later be reversed, the court may treat what is presented as interim protection as final relief and apply the stricter test.

Jurisdiction, natural forum and legitimate interest

MacDonald J drew the governing principles largely from the general anti-suit authorities. As the Supreme Court observed in Prest v Petrodel Resources Ltd, family courts do not operate on a “desert island” where ordinary legal concepts cease to apply.

The jurisdiction is founded on section 37 of the Senior Courts Act 1981 and is exercised in personam against the litigant, not the foreign court. The guiding principle is the ends of justice, tempered by international comity. In a non-contractual case the applicant must ordinarily show both a sufficient English interest in the dispute and that the foreign proceedings are unconscionable, vexatious or oppressive.

The wife succeeded on the first limb. Her needs claim engaged the Maintenance Regulation as it stood when she issued her application. The Court of Appeal had held that she was entitled to choose England for that claim and that the court could not decline jurisdiction on forum non conveniens grounds. England was therefore the natural forum for the needs claim—or at least the existing proceedings gave the court a legitimate interest that required protection if wrongful conduct were shown.

The sharing claim presented greater difficulty. Both parties were born, educated and married in Russia, lived there throughout their 30-year marriage, and were disputing Russian wealth and assets. Nevertheless, because the sharing and needs claims involved the same parties and evidence, England was also the natural forum for the sharing claim. Alternatively, the existing proceedings themselves created a legitimate interest.

This finding did not determine whether substantive relief would ultimately be appropriate under section 16 of the 1984 Act. More importantly for practitioners, it did not decide the injunction application. Jurisdiction, natural forum and sufficient connection provide the court with a basis for intervention; they do not establish the wrongful conduct needed to justify it.

Why the application failed

The wife could not demonstrate to the necessary high standard that the husband’s conduct in obtaining the Russian injunction was unconscionable, vexatious or oppressive.

She relied first on timing. Although sanctioned since 2022, the husband waited until he had exhausted his challenges to the English proceedings before invoking article 248. He accepted that his aim was to bring those proceedings to an end. The court held, however, that waiting to deploy a lawful litigation strategy until it became necessary or most useful did not itself amount to unconscionable conduct. Nor is it inherently oppressive for a litigant to seek a juridical advantage in another forum.

Second, the wife alleged that the husband had obtained the order on a misleading account of his ability to secure justice in England. MacDonald J had previously rejected the suggestion that sanctions prevented the husband from participating effectively in the Part III case. That finding did not, however, establish that the husband had misrepresented the position in Russia. His submissions accurately reflected the general rule under FPR 2010, rule 27.3 that a party must attend unless directed otherwise, together with the licensing framework for legal fees. The wife placed the countervailing facts—including his remote participation and access to representation—before the Russian court. Its conclusion that sanctions impaired access to justice was a matter for that court and the Russian appellate process, not proof of the husband’s wrongdoing.

Third, the potential US$5 billion penalty did not render the husband’s conduct unconscionable. The figure simply reflected the application of a statutory ceiling to an exceptionally large claim. The penalty was not open-ended on the face of the legislation, was subject to appeal, and served an identifiable enforcement purpose. The English court was also cautious about passing judgment on the propriety of another state’s legislation without detailed public-policy argument.

Comity therefore retained its full force. The fact that the Russian order sought to halt English proceedings did not, without more, lessen the restraint expected of the English court.

Procedural warnings

The decision also contains important procedural lessons. The wife knew of the Russian application in February but did not seek English injunctive relief until 1 June, after participating through lawyers in four inter partes hearings and losing on the merits. That delay and participation counted against equitable intervention, even though the court did not treat them as an absolute bar.

The judgment further underlines the need to regularise foreign-law evidence. A Russian lawyer’s opinion letter was excluded because the wife had not sought permission under Part 25 of the Family Procedure Rules. Inviting the court to consider it de bene esse could not circumvent those requirements.

The judge did not decide the husband’s allegations of deficient disclosure at the without-notice stage. Applicants should nevertheless expect rigorous scrutiny of candour, urgency and fair presentation.

Practical implications

The ruling does not shut the door on anti-anti-suit relief in family proceedings. It confirms that the jurisdiction exists and that Part III proceedings can supply the English court with the necessary interest. An applicant must, however, be ready to:

• act promptly, preferably before the foreign anti-suit application has been fully determined;
• distinguish the existence of English jurisdiction from the separate requirement to prove unconscionable, vexatious or oppressive conduct;
• explain whether the proposed order is genuinely reversible or effectively final;
• identify concrete misconduct by the other party, rather than simply criticising the foreign court’s law or conclusions;
• address comity, utility and the consequences for both parties; and
• obtain permission before relying on expert opinion on foreign law.

MacDonald J discharged the injunctions but stayed execution for 21 days to allow the wife to seek permission to appeal. Subject to any appellate intervention, the decision sets a demanding framework: the Family Court may protect international financial remedy proceedings from a foreign anti-suit order, but only where the applicant proves considerably more than jurisdiction, tactical disadvantage, or the existence of a conflicting foreign judgment.