In these pages I have collected about 330 charters and documents relating to the boroughs of the British Isles, which can be dated before the death of King John, and have analysed them into their constituent clauses, and rearranged them in the form of a code. The three parts of the Introduction will furnish all necessary explanations: the first part explains our methods of study and specifies the sources from which the documents are derived: the second part is a short commentary on the code: the third part contains four supplemental essays, in two of which I have attempted to find some general principles underlying the code of municipal privileges, while in a third I have compared some contemporary foreign municipal charters with those of the British Isles. But in these essays, I have dealt only with the problems of the twelfth century, except where express reference is made to other periods: and it does not follow that, because I have hazarded certain opinions with regard to the formation or characteristics of boroughs in that century, I hold the same opinions with regard to the same problems either in earlier or later centuries. In a few instances it will be found that the date of a charter given in the text differs from that given in the list of sources, the reason being that further evidence had come to light after the text was in print.