This article concerns the origins of the idea of action learning, especially the claim by Revans that his Memorandum on "The Entry of Girls into the Nursing Profession" in Essex hospitals written in 1938 was the first step in the development of action learning. Whilst Revans repeatedly made this claim, there is no evidence in the actual words of the Memorandum to support it, and he never explained the basis for his belief. Why Revans saw this paper as a first step is therefore a mystery. In this paper we examine the circumstances of the production of the Memorandum to find possible answers. After discussing the evidence we conclude that Revans' claim is based on the ideas and insights which occurred to him in 1938 in his research and thinking, rather than upon what he actually wrote. We also suggest some defining aspects of action learning can be traced back to ideas first stimulated in the research and production of the 1938 Memorandum, including the importance of first-hand knowledge in tackling organisational problems; the limitations of expert knowledge in complex conditions; the impact of hierarchy on the flow of knowledge; the importance of problem ownership in bring about action for improvement and the primacy of learning in the processes of problem-solving and innovation.