In order to discover the unexpressed intention of the parties, the courts may take notice of the following: trade customs, the conduct of the parties, a course of dealing between the parties and the need to give 'business efficacy' to a contract. It must be emphasised that, where the parties have made an unambiguous express provision in their contract, the court will not imply a term to the contrary: see the House of Lords' decision in Trollope Colls v North West Regional Hospital Board [1973] 1 WLR 601.