Britain occupied Madeira in 1807 originally with the idea of keeping it after the war, it was made a British crown colony for a few months. However, soon after it was decided that it would be returned, and it was in 1814 given back to Portugal.
What if Britain kept the island instead? Would it actually cause any butterflies? Portugal was drawn into WWI because of a German submarine attack on ships in Madeira. Does this affect anything to do with WWI or subsequent history at all?
Also does Madeira become an independent nation or stay a British crown colony today?