Once the spine was reinforced and dried I was able to take the book out of the book press and check to see how strong the sewn-in tapes were - and they're fine! Phew. Then I was able to glue in the end papers: obviously I couldn't do what I would usually do, which is to paste a strip of mull along the folded edge of the end papers and wrap that around the first and last signatures before sewing onto the tapes. Instead, I had to rely on a thin strip of glue along the folded edge of the end papers which adhered them to the first and last pages. I could have simply glued the whole of the first and last pages to the corresponding end papers, I suppose, but the last page of the book was printed with the final columns of the index, which I didn't want to lose!
While the end papers dried in place I made a replacement spine out of thin card, kraft paper and black book cloth. I glued on the fragment of the original spine with the book's title and author.
The kraft paper strip acted as an additional support for the new spine, extending inside the covers. I couldn't extend the book cloth as far because it would have obscured the gold embossed lettering on the front cover. In the photo I haven't trimmed the kraft paper, but once the book block was in place I trimmed the upper and lower edges to match the edges of the end papers.
If I say so myself, I think the end product is not bad for 5 hours' work. The new head and tail bands and the two book marks smarten the book up, and their red and gold colouring is picked up by the beautiful hand-marbled end papers which I bought in Italy - just right for an Italian book!