Charles I of England

Charles I (1601– 1649) was King of England, King of Scotland and King of Ireland from 27 March 1625 until his execution in 1649.

Charles famously engaged in a struggle for power with the Parliament of England. He was an advocate of the Divine Right of Kings, and many in England feared that he was attempting to gain absolute power. Many of his actions, particularly the levying of taxes without Parliament's consent, caused widespread opposition.

Charles I in Atlantis
It was in the reign of Charles I that the pirates of Avalon were destroyed by combined English, Dutch and Atlantean forces.

Charles I in A Different Flesh
Charles I was able to fully adopt the Divine Right of Kings model for England. Rather than fight, his opponents simply fled to North America.

Note: This is speculative--Turtledove did not specify Charles as the king who adopted the Divine Right of Kings, but Charles seems the most likely candidate.