D threatened to refuse to let P’s ship dock unless it entered into an ITF contract with its workers. P sought a declaration that the contracts were voided. HL held that the contracts were voided due to economic duress.
Lord Goff: Economic pressure can amount to economic duress, provided the pressure is illegitimate. It is not a good test to ask whether P has been “coerced” (see Atiyah). Under English law “blacking” (refusing to allow docking) is illegitimate. If an action is legitimised by statute, then it cannot be illegitimate. The illegitimate pressure must be a “significant cause” of D’s act e.g. agreeing to new contract.