4207 may be a clue.
Carrol was a mathemetician and apparently incorporated his ideas into the book as a rejoinder to another school of thought.
As for Lion and Unicorn-perhaps it marks a behind the scenes conflict between the Lion of Judah and another, Unicorn faction.
Intersting that the king proclaims the crown belongs to neither, but to him
The Brit "royal family" are usurpers an latecomers to Britain.
It's true sovereignty has never belonged to them.