My first visit to Ostia was in 1925. I had set out to collect material for a thesis on 'Roman guilds in the light of recent excavations at Ostia'. In two long days among the ruins I found no evidence whatsoever—there was none: it was not until much later that the subject came alive. But from the first I was fascinated by the site, and it has retained its hold; Ostia is my second patria. By 1939 a short book was almost completed. It was stifled by the outbreak of war—mercifully, because by 1945 the subject had been transformed. The campaign of 1938-42 had doubled the excavated area. The evidence now required a different kind of book.
The foundation of the present study was laid during the summer of 1951 at the British School of Rome. I have returned for short visits whenever a busy teaching life and a tolerant wife have allowed; but my last visit was in September 1957. Had I waited longer a better book could have been written, for important problems concerning the course of the Tiber and the form of the Claudian harbour were then in sight of solution, and several hundred inscriptions still remained unpublished. Friends wisely warned me of the dangers of a receding horizon; since 1957, though minor additions have been made, I have concentrated on revision.
With some misgivings I have included the imperial harbours in my study. Their history is so closely linked with Ostia that they clearly form part of a common story, but I have not been able to study them in adequate detail. Many days have been spent in puzzling over the problems of the Claudian harbour on the site, but Trajan's harbour I know considerably less well. I was able to make two visits in 1926 and 1927, but during the critical stages of my work the site was inaccessible to scholars. An unorthodox entry ended, before I had reached my first objective, in humiliation.
In a short preface it is impossible to acknowledge all the kindnesses and help I have received. A wide range of benefactors, from ambas- sadors to schoolboys, must go unrecorded though I remain grateful to them; but certain debts must be mentioned. The most important part of my work was done in Italy among Italians and with their help. Dr. Guido Calza I remember with particular affection and respect. Even . . .