Why have Portugal and the United Kingdom remained allies for so long?
Short answerHe points to dynastic marriage and durable shared interests, especially the fact that Spain was often the principal rival of both states.
NotesMarriage helped establish the Anglo-Portuguese connection, but shared strategic interests kept it useful. For long periods, Portugal and England or Britain faced Spain as their most consequential nearby rival. Cooperation reduced risk for both sides without creating the same degree of direct competition between them. The alliance survived because its original diplomatic tie aligned with persistent geography.