D agreed with P, when in the SAS, not to publish books disclosing his activities upon retirement. He then did so and P sued him for breach of contract, and D mounted a defence of economic duress, saying that if he had not agreed to the contract, he would have been demoted. Privy Council held that there was no illegitimate pressure and therefore no economic duress.
Lord Hoffmann: The two elements of economic duress are: (1) pressure amounting to compulsion of the will of the victim, and (2) the illegitimacy of the pressure”. He cites, with approval, the minority statement in Universe Tankships inc of Monrovia that many choices in life are subject to overwhelming pressure, but that this does not necessarily negate consent in law. Lawful pressure does not necessarily equal legitimate pressure and the parroach to be adopted is determining legitimacy is that of Lord Scarman (above): nature of pressure and nature of demand. Here, the nature of the demand was well-motivated (to stop unauthorised disclosures) and it was therefore reasonable for the MoD to decide that anyone unwilling to confine themselves to these conditions was unsuitable for the SAS.