For what it’s worth, I found this when I asked Google about Lewis and Catholicism. It’s from a publication called Calvary Contender which seems to be a little broadside put out by a Baptist church in the southern USA…
TOLKIEN, C.S. LEWIS, CATHOLICISM—Jill Saunders, writing in the Mar.-Apr. Canadian Revivalist, says there is much evidence of J.R.R. Tolkien’s devout Roman Catholicism. In a letter to his son Michael, he said: “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 [the Mass]”. Tolkien’s wife had to convert to Catholicism on their marriage, and their son, John, became an ordained priest. Saunders adds: “It is interesting that C.S. Lewis converted to Christianity through Tolkien. [They] were close friends for most of their lives and belonged to a literary group called The Inklings, who met weekly at an Oxford pub to drink, smoke, and discuss each other’s stories. While Lewis was an Anglican, he held some R.C. views including its doctrine of purgatory and the Mass; he also requested the ‘Last Rites’ of the R.C. Church on his deathbed.” Tolkien’s *Lord of the Rings *was basically a religious and Catholic work.