Please forgive me if I take the wording of the question too literally, but I believe I am correct in saying that it was never "illegal" in England to own or read any kind of book, including the works of Luther. Instead, English printers of books were required to apply for a license to print any book, so that official censors could either approve the text, require changes to the text, or deny the license altogether. Similarly, books imported from the continent were expected to pass through something like customs screening so as to weed out disapproved texts. And while it was the goal of the governing authorities to prevent the domestic printing or importation of disapproved books, they never sought to prevent people from owning a particular book if it happened to be either printed or imported. But as you can imagine, even the seemingly simple task of monitoring domestic printing and importation was far more than the English bureaucracy could ever handle. Books were often printed without license and imported without approval. They were sold quietly rather than in the booksellers' shop windows.
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