Maybe just do something destructive. Just take a Sharpie permanent marker and write "ROYAL LIBRARY" on the bottom plane of the book pages. Granted, that's a fl

Maybe just do something destructive. Just take a Sharpie permanent marker and write "ROYAL LIBRARY" on the bottom plane of the book pages. Granted, that's a flippant proposal. And it wouldn't work on certain books, where the edges of the pages are gilded. (I wonder if many/most books from those days had gilded edges?) The Sharpie is just one idea. I'm sure there are much more clever, simple, obvious permanent methods that could be used in appropriate circumstances. The main point is to permanently and clearly mark the entire book. Yes I know this would destroy the "value" of the book in many people's eyes. But I'd like to ask the Royal Library this question: Would you rather have in your possession the Louvain edition of Thomas More's Utopia, with "ROYAL LIBRARY" written in Sharpie on the bottom, or would you rather that the book had been sold at Christie's for 140,000 GBP, and you have nothing? I know which I would choose. But I'm not an art historian.