It was from outside academia that he entered into communication with the ‘high priest’ of British theoretical physics, P.A.M. Dirac, challenging him with the idea of a statistical basis of quantum mechanics. Their correspondence forms the core of this book and opens up an important and hitherto unknown chapter for physicists, mathematicians and historians of science. Moyal’s classic paper, ‘A statistical basis for quantum mechanics’, also reproduced here in full, has come to underlie an explosion of research and to underpin an array of major technological developments.