Estoppel can prevent a party from asserting their strict legal rights (acting as a shield), but it cannot be used to create new legal rights or claims that did not previously exist (acting as a sword).

1. CONSIDERATION

12. Consideration must be sufficient but need not be adequate Mountford v Scott (1975) Paid $1 for an option to purchase a house – deem good consideration Chappell v Nestle (1960) Three wrappers from the defendant’s chocolate - deem good consideration

14. Duty under a contract with the same party If Promisee performs existing contractual duty owed to Promisor this is not sufficient consideration. Stilk v Myrick 2 sailors deserted ship, captain promised the rest of crew extra wages if they sail ship back home. Held : crew already bound by contract to meet normal emergencies of voyage and were doing no more than their original contractual duty in working ship home. Hartley v Ponsonby nearly half the crew left. Sailors exceeded their existing contractual duty.