This comes from The Highways and Byways of Oxford and the Cotswolds:
“In 1363 the Staple, as the licensed mart for the sale of English products was called, was, after several changes, definitely fixed at Calais, and here buyers from all parts of the continent would congregate. We can in imagination draw a picture of the appearance which the High Street of Campden would have presented at this period about shearing time. Droves of pack-horses laden with wool consigned to Grevel and other merchants, would be seen slowly filing through the town to the Woolstaplers’ Hall, a 14th century building still standing, with its adjacent warehouses. Here the wool would be sorted and made up into bales of the orthodox size called sarplers and pokes, while samples would be passed from hand to hand, to be criticised and appraised by the assembled merchants: bids would follow and a considerable quantity would change owners, as corn does now-a-days in a modern corn exchange.
Before Grevel’s time most of the bales thus sold would have sooner or later found their way to the continental market. But ion his time a change had begun, the effect of which was to diminish the foreign exportation of the raw material, and which ended in stopping it altogether. This was the rise of the native clothing trade. Anxious to improve the domestic manufactures, Edward III encouraged the settlement of Flemish artisans in the country, and under their influence cloth of an excellence hitherto unknown except as imported goods began to be made in several pars of England. In Gloucestershire, the home of the new industry was the valley of the Stroud Water and its numerous affluent, and we can have no doubt that a large proportion of the Cotswold wool, which had formerly been shipped to Flanders, was now manufactured into cloth at home. At last the home-made cloth itself began to be exported, till the cloth industry became so flourishing that under Elizabeth the export of wool in the raw state was altogether forbidden. in the long run, this changed state of affairs, conducive as it was to the general prosperity of the country, proved fatal to the prosperity of Campden.Though conveniently situated as a centre for the collection and distribution of the raw material, the town was deficient in that abundant supply of water-power which attracted the new manufacturing interest to the copious rivulets of the Stroud valley, and with certain qualifications to be noticed directly it became from the accession of the Stuarts onwards a purely agricultural country town. ”