On which basis did Idi Amin claim to be uncrowned king of Scotland?

As much as he has been labeled crazy by almost everyone, Idi Amin had once been narrated to by a white man, (apparently who didn't believe the windsors as the true heirs of the british monarchy), about the existence of black people in europe centuries ago and who had been kings and nobility in europe in the old days. Of particular interest to him came to be the Jacobites and the theory that they were of a certain black origin, the house of stuart (swearth in old english meaning dark complexion) from Scotland who once ruled Great Britain Ireland and Wales. Idi Amin henceforth was fascinated by the possibility of blacks kings in ancient europe (in particular scotland due to the Jacobites), and decided to label himself a continuity and the current remaining descendant of that ruling dynasty, hence The Last King of Scotland.

Source of this quotation was at Yahoo Answers, which has closed down.

His passionate interest in Scotland developed over a number of years, considering that Uganda and Scotland had been similarly ill-treated by English imperialists. He offered to take on the kingship of Scotland, in defiance of the official status of the United Kingdom, but the offer was never taken up, hence he remained an uncrowned king.

https://www.quora.com/How-did-Idi-Amin-get-the-title-of-Last-King-of-Scotland

This was only one of the string of self-aggrandizing titles he assumed. He officially designated himself

His Excellency President for Life, Field Marshal Al Hadji Doctor Idi Amin, VC, DSO, MC, CBE, Lord of all the Beasts of the Earth and Fishes of the Sea, and Conqueror of the British Empire in Africa in General and Uganda in Particular.

https://www.bbc.com/news/magazine-18855099