What kinds of interaction take place in a history department? What might be their value? Between 1999 and 2003, Simon Letman, then history teacher and Director of Studies at The Royal Hospital School in Ipswich, set out to discover how the rich variety of between-teacher- interactions, so much a feature of the department he had worked in for nearly a decade, might have informed his own practice and that of his colleagues. What he discovered was that interactions are perhaps the single most important element in allowing teachers to make sense of the complex and challenging world in which they function and one of the most important elements in the development of their craft knowledge.