This book has been long in the making. When one of the authors (M.D. K.) first began to study English monastic records in 1926 he adopted the practice, for his own interest and information, of noting any contemporary reference to an abbot or prior. He took for his limiting dates 1066 and 1216. In the event, the opening date has been pushed back to 940, the refoundation of Glastonbury which heralded the great revival. The entries were made in a series of large notebooks, divided among the orders with a page for each house. When, about 1931, the names had already accumulated in some strength, the compiler, on a visit to Cambridge, called upon Dr (later Professor) Z.N. Brooke in his house in Milton Road to tell him of this and other projects which were under way. Dr Brooke was, as always, courteous and helpful, but did not appear to take any special interest in the lists. In due course, however, when correspondence passed, he began to send notes of abbots he had come across in his own reading. At last in May, 1942, a formal suggestion of collaboration was made by M. D. K. and accepted by Dr Brooke. This was followed by a meeting in London, which was attended by C. N. L. B., still a schoolboy, but already interested in problems of chronology. The Brookes carried off the notebooks to transcribe them, and C. N. L. B. left them on the top of a bus. Fortunately, a swift pursuit on foot led to their recovery; and the pursuit has continued ever since, though rarely at the original pace or with the same hazard.