COT3s Can Bar Future Whistleblowing Detriment Claims, EAT Rules

In Darlington v London Borough of Islington & Anor [2026] EAT 11, the EAT held that a COT3 settlement agreement concluded through ACAS can bar future whistleblowing detriment claims linked to earlier protected disclosures. The claimant had previously settled whistleblowing allegations but later alleged that a refusal to appoint her to another role within the same local authority was connected to those disclosures. The EAT held that where a COT3 is drafted in clear, objective terms to include “future claims” or events occurring after the agreement, it can validly prevent such claims, even if the alleged detriment arises post-settlement. However, the judgment emphasised that while the right to pursue compensation for detriment may be waived, workers cannot be prevented from making future protected disclosures under section 43J of the Employment Rights Act 1996.