The authorship of The copy of a letter written by a Master of Art of Cambridge, or ‘Leicester's Commonwealth’ as it became known, was successfully kept secret when it appeared in 1584. It was common policy for Catholic writers to publish their books anonymously during this period, especially political works, but with one as libellous and seditious as ‘Leicester's Commonwealth’ it was necessary to take every precaution to conceal theidentity of the author. The Earl of Leicester, grossly insulted in the pamphlet, tried hard to find out in France – where the book was known to have been printed – who had written it, and it was reported that he had sent an assassin to the continent to deal with the author. When the book first came to light in London, Walsingham confidently ascribed it – ‘the most malicious written thing that ever was penned sithence the beginning of the world’ – to Thomas Morgan, an agent of Mary Stuart in France, assisted by three other Catholic exiles, Lord Paget, Charles Arundell and William Tresham, but this was no more than a guess and did not convince Leicester. It was not until fifteen years later that the authorship of'Leicester's Commonwealth’ again aroused interest, when a group of English Catholic writers known as the Appellants began to ascribe it to their enemy, the Jesuit Robert Persons. Persons refused to acknowledge authorship, but it was generally accepted that the book was his, and when in 1641 it was republished by a Protestant it was clearly ascribed to the Jesuit. Less certainty was entertained by later historians, but the difficulty remained: if Persons had not written the book, who had? This problem was solved in 1957 in an article by the Jesuit historian, Leo Hicks, who, developing an idea of his older colleague, J. H. Pollen, ascribed the book to a Catholic exile named Charles Arundell and denied that Persons had played any part in its composition. This ascription has been unanimously accepted by later scholars. I wish in this brief paper to question Fr Hicks's findings and to argue that Persons played the major part in the compilation of the book.