Not claiming it makes a lot of sense, Google is your friend there. Charles III seems to support the claim, and has invited him into the coronation ceremony. Simon Abney-Hastings, 15th Earl of Loudoun

This may help.

The guest list of this weekend's coronation of King Charles III includes an Australian who may have a claim on the throne. Simon Abney-Hastings is the earl of Loudon. Some historians say there are questions about the legitimacy of the birth of King Edward IV way back in the 15th century, and that the line of succession should have gone instead through Abney-Hasting's ancestors, making him the rightful ruler. But there will be no coup because the earl says it's all cool.