This presents a combination of essays written from about 1970 onwards together with some additional material. It consists of 20 items. Of these 20 items, 13 have appeared in accessible places hitherto; two have appeared in inaccesible places and a third has appeared only in truncated form. Five items are review articles and represent responses to the major works on the period that have appeared over the period. For this collection, the author has written three essays, one introducing each of the three sections. All the essays have been left as they were originally written, bar the updating of references to works not published at the time of original publication.