Research to date is rich in its claim that practice development in schools, and the leadership and professional learning that it demands, requires relational trust. However, reasonings for, and understandings about, relational trust are described mainly in general terms, leaving its complexity and multidimensionality implicit. Much trust research in schools has focused on principals, neglecting fulsome characterisations of relational trust as it is engendered in practices by middle leaders often responsible for leading school-based professional learning. This article addresses an empirical void in expositions outlining the intricacies of relational trust. Results advance previous ethnographic research conducted in primary schools delineating five interconnected dimensions of relational trust: interpersonal, interactional, intersubjective, intellectual and pragmatic. Findings from a two-year replication study conducted in secondary schools are presented. Deductive thematic analysis of semi-structured interviews with educators from three Australian secondary schools adds analytic depth to previous research. Revealed is a "doubleness" in how relational trust, in five dimensions, was found to not only form conditions for middle leaders to consciously build and cohere, protect and preserve communicative spaces for developing trust; but that this trust reciprocally generated conditions for realising the transformational goals of school-based professional learning.