This book is what is called in the museum world an exhibition catalogue, which are as a matter of course released alongside major exhibitions; Kate wrote the preface. Hold Still was an exhibition from 2020 of 100 photos chosen from a photo competition. It was put together by the NPG and Kate, their patron, and was online and on billboards due to the pandemic. They would have planned for the book when they first put together the idea for the photo competition and exhibition. So it's been in the works a long while. The publication date has likewise been known for a long time. Well before Meghan's children's book was announced.I don't normally comment on Kate, Will or Harry but out of curiosity did Kate start writing her book first or was it Meghan?
I saw that Kate recently has been leaving copies of her book across the UK. Honestly I find it a bit much, its like they are constantly are trying to outshine/prove they are better than Harry and Meghan. Seems strange that as soon as Meghan released her children book, Kate is leaving her book everywhere with some letter in.
Interestingly, It's also not the first book Kate's written a preface for. On my shelves I have a GCHQ Quiz book she wrote a preface for from a few years ago now! Linked to a Bletchley Park anniversary I think. The RF are often involved in books linked to their patronages.
The leaving books around the UK is an initiative of a organisation called Book Fairies, and is focused on sharing good books and literature around the world. https://ibelieveinbookfairies.com/