Good point. King Derek I sounds good for an England set in 2955. Simple, British, yet futuristic. King Thomas makes it sound like the setting is more medieval-ish.
Thanks! Other suggestions....Ryan, Aaron, Clint, etc. I'd go for a unique name, something that hasn't been used for historical real-life kings already.
Gee, no one has mentioned Charles, even though there have been two of them. Of course, it has been about 350 years, and neither one was what one might call a success. Charles I rather lost his head.
I'd stay far, far away from a name that has already been used for a king (okay, I"m sure Thomas probably has at some point, so my bad). Readers will just associate your king with that king.