This volume was the inspiration of the mathematical logician Barry Cooper. In 2007 he was already planning a conference to mark the centenary of Alan Turing's birth, but this was just the start of his huge and energetic dedication to a renaissance of Turing studies. In 2009, while taking on the project of a new critical edition of Turing's papers, he also raised with Cambridge University Press (and with me) an idea for a book about ‘Turing and the future of computing ’. After correspondence with David Tranah and Silvia Barbina of the Press, Barry and I conceived it as an opportunity for leading scientific thinkers to bring exciting and challenging aspects of Turing's legacy to a wider readership.

In 2010, we settled on the title of The Once and Future Turing, and extended invitations on this basis. Our enterprise rested on Barry Cooper's networking power, arising from his role as chair of Computability in Europe and countless conference committees. More profoundly, it was steeped in his intellectual quest to see logic interact with new advances in physical and human sciences. His very individual vision of ‘computing the world’ is prominent in the subtitle and introductions for the five Parts of the book, which were mainly his responsibility. My own contributions, including the overall introduction, revolved around the Turing Once. Barry wrote for the Turing Future.

Unfortunately, just as this book was in the last stages of preparation, he met a rather sudden death. It was a particular sadness for him that he was not able to see the publication of this book. He expressed heartfelt thanks to everyone involved at Cambridge University Press, a gratitude I keenly share, and, above all, to the generous work of the distinguished and ever-patient contributors. Their writing, in so many different ways, reflects the magic of time and human life and will speak to a future that neither Alan Turing nor Barry Cooper could live to see.