In the course of his researches for the _History of English Law_ Maitland had been drawn into the unfamiliar region of ecclesiastical jurisprudence, a department of knowledge once of the highest importance throughout Europe, but, save for one exception, fallen into complete desuetude at the English Universities ever since the study of the Canon Law was proscribed by Henry VIII. The exception was provided by William Stubbs. That great master of medieval history had from his Oxford Chair delivered and subsequently published two lectures upon the Canon Law in England. A stout patriot and a high Anglican, Stubbs was concerned to exhibit the continuity of the English Church before and after the Reformation; and both in his Oxford lectures and in a famous report drawn up for the Royal Commission on Ecclesiastical Courts he gave the weight of his authority to the opinion that the Canon Law of Rome, though held to be of great authority in England during the Middle Ages, was not recognised to be binding on the Courts Christian of this country. The verdict of so fine a scholar was eagerly welcomed by men of High Church opinions. If the Canon Law was not binding, then the Church of England was never in the full sense ultramontane, and the changes of the sixteenth century did not amount to revolution. Zealots went further still. There were those who, as Maitland wittily observed, seemed to believe that the Church of England was "Protestant before the Reformation and Catholic afterwards." In the quarrel between the Highs and Lows Maitland had no interest. Then, as always, he was a dissenter from all the Churches: but historical truth was precious to him, and in the course of the summer of 1895, while engaged in the preparation of a course of lectures upon the Canon Law, he became gradually aware that the received opinion could no longer stand. The agent of his conversion, if conversion it can be called, was the _Provinciale_ of William Lyndwood, a popular text-book written in 1430 by the principal official of the Archbishop of Canterbury, and representative of the accepted opinion in the century preceding the Protestant Reformation. The following letter to Mr R. L. Poole explains the genesis of a book which has permanently deflected the current of historical opinion. * * * * * HORSEPOOLS, STROUD. _15th August, 1895._