In 2004, the UK government launched a new programme for early years leaders in England--the National Professional Qualification in Integrated Centre Leadership (NPQICL). In collaboration with the National College for School Leadership, Pen Green led the development, pilot and rollout of this M-level training programme, which by 2006-07 involved 17 learning communities across the nine English government regions. This article analyses the ways in which 788 NPQICL participants differentially experienced the same professional development opportunity. Participants completed evaluative questionnaires at 10 different points over each year of the one-year programme. The data highlight some of the tensions implicit in sustaining a high-quality professional development opportunity across a national rollout. The central question was: What can participants' evaluative feedback tell us about the strengths and weaknesses of the national rollout? Answers emerged regarding how the strengths of the pilot programme might be sustained, including generative pedagogical isomorphism characterised by optimum levels of challenge and support of, and by, rollout tutors and mentors. (Contains 7 figures and 12 tables.)