This thesis explores differences in the role of non-executive directors (NEDs) in small and medium-sized enterprises (SMEs): between the literature and SME practice and between the perceptions of SME NEDs and their managing directors (MDs). The explanation of these differences contributes to a richer understanding of the development of NED role trust in UK SMEs, identified as a gap in our understanding. Extending earlier research by Berry and Perren, the thesis makes a contribution to knowledge by developing a theory to explore and explain the temporal and contextual nature of the dyadic relationship between NEDs and MDs in SMEs.