The Treaty of Union of the Two Kingdoms of Scotland England.
The above continually refers to " .... that the succession to the Monarchy of the United Kingdom of Great Britain ....

and "... That the United Kingdom of Great Britsin shall ....

and " ... a that all parts of the United Kingdom ...

and " ... that part of the United Kingdom called Scotland ....

There are innumeral examples of the terms Great Britain and the United Kingdom in the above Treaty.

The United Kingdom was formed between The Kingdom of Scotland and the Kingdom of England, remove one and there IS no United Kingdom.