This is what indexes are for - looking up stuff quickly to compile information about a subject and what other people have said about it, or in this case, the late Queen. And I hope that all the books used the proper Elizabeth II, Queen style entry for her maj.
‘Brown gathered these insights via a rather “mad” and “pedantic” system, which was to look up “Queen Elizabeth” in the index of every 20th and 21st-century book in the London Library’s memoir and biography section, and then group them in themes.’ www.thetimes.com/article/bc2d...
Yachts, tantrums and horses: the acclaimed biographer Craig Brown reveals what he discovered about the former monarch to write his quirky, honest portrait of her
I wonder how many of those ERII index entries are really quite minor mentions, but they went in because she was the Queen?