William Oughtred's Clavis mathematicae, first published in 1631, was regarded for the remainder of the seventeenth century as a classic text in algebra, reprinted, translated, and explained for over 70 years. Yet its content was limited, its style obscure and its notation old-fashioned even when it was first written, and it now seems extraordinary that it should have had such a long life. The early success of the book, and the great esteem in which Oughtred was held by contemporary and (...) later mathematicians, can only be understood in the light of the general state of algebra teaching in England during the first half of the seventeenth century. In later years the book was kept alive by the efforts of one of its greatest admirers, John Wallis. The aim of this paper is to set the story of the Clavis into the wider context of English algebra, and the political background of the time. (shrink)