The markup in this work had been diverging from validity for a long time, so a whole stack of errors had accumulated, and the overall hierarchy was no longer easily discernible. I've worked through the whole text with the primary aim of fixing the hierarchy, and we now have a valid document. However, there are a number of things that still need to be looked at. I'm recording these here so that PG and I can sit down and work through them:

• Forme works are only occasionally marked up. We need to make sure that all page numbers, catchwords and signatures are caught and tagged as <fw>s.
• Stanza breaks are not usually marked; the run of lines continues unbroken, inside one <lg> tag, through what are clearly paragraph-style breaks. We need to identify all those breaks, and then close and re-open <lg> elements.
• Related to the above, there are some lines at the beginning of verse-paragraphs which are indented. These lines need rend="text-indent: 2em;" or whatever the measurement is.
• PG made a valiant attempt to use <salute>, <closure>, <sign> and <name> tags in the prefatory material (which is largely dedications, so has a lot of this kind of thing in it). However, the markup structures we're using make this difficult, and none of the existing formulations was valid; because of the need to render the code valid before we go any further, I've pulled out those tags and used plain <p> tags, with some <name> tags left in place, for those locations. However, the intent was correct, and we must revisit those areas of the text to devise and implement the correct formulations for them (and then handle them in the XSLT output).