When is a term implied in a contract?

When the courts are implying a term into a contract, like reasonable notice upon termination, heed should be paid to MacKinnon L.J. in Shirlaw v. Southern Foundries (1926) Ltd., [1939] 2 All E.R. 113 where, at 124, he said: Prima facie that which in any contract is left to be implied and need not be expressed is something so obvious that it goes without saying. Thus, if, while the parties were making their bargain, an officious bystander were to suggest some express provision for it in their agreement, they would testily suppress him with a common: “Oh, of course.” When dealing with a continuing relationship the above test can be applied at various stages of that relationship.