This decision considers the somewhat ambiguous test in English law regarding unilateral mistake.
Mrs Justice Ellenbogen provides some welcome, albeit obiter, clarification: the defence of unilateral mistake can only succeed where a party is able to demonstrate that their counterparty had actual knowledge of the mistake. She clarified that constructive knowledge is insufficient – the consideration of what a reasonable counterparty ought to have known is simply one of the tools available to the court when evaluating, on the balance of probabilities, whether a counterparty in fact possessed the requisite actual knowledge.