Thank you all very much for the quick response - I did trawl the letters,
but not well enough. This will help me better formulate a supposition on a
short paper I'm preparing.
In our research for _The J.R.R. Tolkien Companion and Guide_, we found no
evidence that Tolkien ever visited Northern Ireland.
Christina Scull and Wayne Hammond
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The Scull and Hammond J.R.R. Tolkien Companion and Guide is a wonderful
resource for answering questions like this. The entry for Ireland in the
Reader's Guide quotes a letter he wrote in 1971 that says he has never
been in the North.