Katharine Burn has a long-standing interest in history teachers' professional learning--not just the ways in which experienced teachers can support beginners, but how teachers at all stages of their career can be encouraged to go developing their practice. In this article, which draws on a number of small-scale research projects, she illustrates the range of ways in which those who have formal responsibility for others' learning (such as heads of history and history mentors) and those who do not can each work effectively to help shape genuinely expansive learning cultures in their departments.(Contains 6 figures.)