This paper presents the outcomes of an empirical investigation into the validity of Bryan Cunningham's thesis that the effectiveness of teacher mentoring is enhanced by a supportive institutional framework comprising eight 'architectural design features'. It draws upon analyses of data from a mixed methods study of mentoring in the English Further Education sector. Data were generated via 40 semi-structured interviews with teachers, mentors and other stakeholders, and a national online survey of teachers of all subjects/vocational areas, completed by 392 respondents across all nine regions of England. The paper presents a reconceptualisation of the architecture for mentoring, which encompasses both a mentoring substructure and superstructure. Cunningham's institutional architecture (reconceptualised as a mentoring substructure) is extended through the identification of additional design features, while limitations of the concept of an institutional mentoring architecture are exposed and evidence presented to show that a complementary superstructure is a necessary additional means of seeking to achieve optimally effective mentoring. A new research agenda is proposed to explore the extent to which the proposed mentoring substructure and superstructure are applicable in different professional and international contexts, and to identify common features of optimally supportive mentoring superstructures.