I was intrigued by one minor detail though. Tolkien is very precise about the date of the last major Goblin attack - 1453 - which rather suggests a link with the Ottoman Turks who famously stormed Constantinople in that year. Now we have to be careful here: Tolkien claimed to hate allegory (though there is more than a whiff of it in stories like Farmer Giles of Ham and the wonderful Leaf by Niggle). The simple fact that the Goblins return to the North Pole during the dark days of World War II suggests that we cannot simply equate the Goblins with the Ottoman Turks. However, this simple fact also suggests that Tolkien's imagination was rather more allegorical than he sometimes claimed or would have liked.
One word of warning. You don't get all the letters in The Father Christmas Letters or even, I think, in some editions of Letters from Father Christmas, which can be rather frustrating.
Indeed, despite the enormous number of books published by and about Tolkien, there are still some gaps. I look forward to the day, for example, when we get a Collected Letters. What we have at the moment is only a selection with some significant lacunae. Take this example, for instance:
"Out of the darkness of my life, so much frustrated, I put before you the one great thing to love on earth: the Blessed Sacrament..... There you will find romance, glory, honour, fidelity, and the true way of all your loves upon earth, and more than that: Death: by the divine paradox, that which ends life, and demands the surrender of all, and yet by the taste (or foretaste) of which alone can what you seek in your earthy relationships (love, faithfulness, joy) be maintained, or take on that complexion of reality, of eternal endurance, which every man's heart desires."(pp.53-54)
I'd love to know what comes at the end of that first sentence. But, even with the gaps, these letters are really wonderful.