Your challenge, if you choose to accept it, is as follows:
With a PoD after the Treaty of Paris, have a black man of African descent placed on the throne of the United Kingdom.
The requirements are:
The United Kingdom, at minimum, must include the majority of the territory of England.
The monarch must be of at least 50% black African descent.
The monarch must rule in the British Isles.
The monarch must retain effective control of the territory of the United Kingdom, or at least its home nations, for a period no less than one year.
Bonus points if the monarch has a legitimate claim to the throne and if the monarch is born in Africa.