Why was King Charles III holding a blue book during his declaration?

My wife and I are puzzled. During his declaration at the Accession Council, he held a blue book in his right hand. Why? What is it? It doesn’t look big enough to be a Bible or anything like that. It looks more like a personal calendar book.

Could have been a prayer book, or a set of the four gospels.

Wasn’t that a binder filled with draft Orders-in-Council for him to approve?

According to the commentator during the live coverage of the BBC, it was a New Testament.

Interesting. Makes sense. Thank you!