N-of-1 Randomised Controlled Trials (N-of-1 RCTs) are an important recent addition to the repertoire of study designs in health psychology and behavioural medicine. They provide an opportunity to evaluate the effect of interventions on one individual by randomly allocating different time periods to repeated intervention and control conditions and comparing responses. N-of-1 methods can be used to test health behavioural theories and interventions in line with the Medical Research Council’s recommendations for the development and evaluation of complex interventions (Medical Research Council, 2008) and recent guidance has been published to facilitate the assessment of quality and reporting of N-of-1 RCTs (Vohra et al., 2015) reflecting the increasing focus on quantitative single-case methods.