Here’s a follow-up thought on the subject. Since Wilhelm had already become Kaiser in 1888, his accession to the British throne in 1901 would in principle have created a situation in which he ruled two countries simultaneously: Germany as Kaiser and Britain as King. So Germany and Britain would have turned into a dual monarchy like Austria-Hungary, of which Franz Joseph I was both Emperor and King. This could be the basis for a rather interesting alternate-history version of the Axis & Allies 1914 WWI game, though I can’t make up my mind who would have gone to war against whom in this scenario. One thing is certain, though: Wilhelm would have loved to get his hands on the Royal Navy, since he’d always been jealous of Granny Victoria’s big, shiny fleet.
This is interesting indeed, but I do wonder if the constitution of the United Kingdom would allow for a dual monarchy? I think the more likely option here would the British telling Wilhelm that he would have to give up being Kaiser if he wanted to be king of Britain and I think we both know that Wilhelm would have never done that. The next option would have been that have Princess Royal Victoria’s second born, Princess Charlotte take the thrown after her mother. This would have made for an interesting change, and while I don’t think it would have altered the course of the UK too much, it may have prevented the Entente Cordiale from being signed in 1904. This initiative was largely conducted between the Prince of Wales Albert Edward (who became King Geroge the VII). IF we remove him from the picture then it becomes doubtful that the agreement would have come to pass.
It’s all ideal speculation but it sure is fun