The article argues that preparing to be, in Shulman's words, "ready, willing and able" to teach with ICT can be supported by an integrative framework of teacher professional knowledge which recognizes connections between subject domain knowledge, the didactic relation with information and communications technology (ICT), and an openness of mind in the moments of teaching, similar to improvisation. A study of teaching with ICT in an English primary school illustrates links between understandings of Didaktik and improvisation as teachers draw imaginatively upon subject knowledge to represent content and purpose appropriately for their pupils. The article discusses a relationship between understandings of Didaktik and improvisation, and the importance of conceptual subject domain knowledge in primary teacher education at a time of debate about curriculum, technology and professional knowledge. (Contains 2 figures.)