While a great deal of attention has been given to evaluating how well policies are implemented, that is, how well they are realised in practice, less attention has been paid to understanding and documenting the ways in which schools actually deal with the multiple, and sometimes opaque and contradictory demands of different "types" of policy. This paper addresses the question of how it is that some education policies "fail" to translate into a continuing and effective set of practices in schools, and instead, are subjected to processes of dissipation and mutation. In this paper, we take as our case personalised learning (PL) launched in England in 2004. In understanding complex processes of enactment, the challenge is to understand how policies differ and analyse why some policies "work" in ways that are unexpected--not as failures of implementation but as mutations. As a "case" of policy dissipation, PL highlights the changing relationships between national and institutional imperatives, and the creative mutations to which some policies are subject within schools. It is not that they have no effects, but rather their effects are marginal or nuanced rather than immediate and obvious.