I hope this is the right place to ask, but I have a question about using regnal numbers in writing. In a chapter about Henry III, for example, should I include the III every time I refer to him, or is it acceptable to use Henry III the first time, and then just Henry afterwards?
Assuming you're only talking about Henry III, I would use Henry III first time, and Henry thereafter. If you have to talk about multiple Henrys (Henries?), then you are going to have to distinguish them.
I have faced a similar problem recently in my thesis writing. There's two Basils, two Eusebius(es), at least two Gregories. I distinguish them whenever there's a chance of confusion.