Once Tolkien had made a thorough study of the history of English and its literary artifacts, he discovered the native English had actually lost their mythology when the French came during the Norman conquest. So Tolkien became interested in trying to figure out whether he could restore some of that mythology. Eventually he gave up the idea that he would be restoring an actual mythology for England. But this mythological backdrop continued to permeate everything that he wrote for the rest of his life.Tolkien’s paternal ancestors apparently arrived in England half a millennium after the Norman Conquest, but he identified with the earlier Anglo-Saxons. The notion that England lost its original Good Things to the Norman Conquest was also part of Whig political thinking in the eighteenth century. So in that respect The Lord of the Rings is a cultural cousin of the Declaration of Independence, sharing an intellectual root.
Fisher also notes that The Hobbit was originally more tweely English and contemporary in its first edition:
Tolkien was actually an inveterate niggler. He constantly tinkered with his works. For most people, The Hobbit that they know today is the version that includes all of these changes and revision. But if you read the first edition of The Hobbit you see all kinds of strange things, like references to policemen on bicycles, references to Lilliputians, a reference to the Gobi Desert, the wild wireworms of the Chinese, all of these references to the real world. After the first edition, Tolkien cut all of those references and made it more of its own separate world.Eventually, it appears, Tolkien tumbled to the fact that he was creating a mythology not for England but for himself.