This thesis examines how the legal conception of the consumer is constructed, by analysing instances of judicial application of three fairness tests; the unfair terms test (Consumer Rights Act 2015), the unfair practices test (Consumer Protection from Unfair Trading Regulations 2008), and the unfair credit relationship test (Consumer Credit Act 1974). The approach of the court when constructing the conception of the consumer is assessed within a theoretical framework which distinguishes between an abstract approach to conception (based on assumptions regarding consumer interests and traits), and a behaviourally informed approach (based on the findings and methodology of behavioural economics). The normative ethic underlying the courtsâ choice of approach is considered, as is the impact that reliance on different approaches has on legal outcomes produced under the three tests. The approach of courts is contrasted with that of regulators who play a significant role in the enforcement of consumer protection law. It is suggested that the approach adopted when constructing the conception is important because it affects the legal systemâs treatment of actual consumer interests. It is suggested that there is a degree of uncertainty regarding the correct approach to conception, and evidence of both abstract assumptive and behaviourally informed approaches is detected. This is contrasted with the behaviourally informed approach of regulators. It is argued that there are advantages to the adoption of a behaviourally informed approach for the purposes of assessing fairness in the context of consumer law. It is suggested that this could produce a more satisfactory form of legal reasoning, which will provide greater scope for protective legal outcomes and a more effective discourse between regulators and the courts. In turn, it is suggested that courts should place emphasis on the responsibility of suppliers when assessing fairness to allow them to maintain an appropriate balance between consumer and supplier interests.