In the Middle Ages, Great Yarmouth was a town of considerable economic and strategic significance; in 1334, it ranked fourth in English provincial towns in its wealth. This work examines in detail the construction and, more especially, material composition of the Great Yarmouth town walls. Contents: 1) Great Yarmouth: geographical, historical and economic background; 2) The structure and composition of the walls; 3) The town wall: a modern geological perlustration; 4) The wall fabric an analysis; 5) Other defensive systems: early walls, towers, rampires, pseudo-ravelins and a moat; 6) The financial provision for wall construction; 7) Records of expenditure on wall construction, modification and repair; 8) Reservations and conclusions; Glossary, references and ancillary bibliography.This study takes a geological approach to the study of the flint walls of Great Yarmouth, generally considered to have been constructed when the town was at the height of its power and wealth in the fourteenth century.