It was of this trade above all that the gild merchant of each town possessed the regulation. Merchants from another town were treated much the same, whether that town was English or foreign. In fact, "foreigner" or "alien," as used in the town records, of Bristol, for instance, may apply to citizens of London or Oxford just as well as to those of Paris or Cologne. Such "foreign" merchants could deal when they came to a town only with members of the gild, and only on the conditions required by the gild. Usually they could buy or sell only at wholesale, and tolls were collected from them upon their sales or purchases. They were prohibited from dealing in some kinds of articles altogether, and frequently the duration of their stay in the town was limited to a prescribed period. Under such circumstances the authorities of various towns entered into trade agreements with those of other towns providing for mutual concessions and advantages. Correspondence was also constantly going on between the officials of various towns for the settlement of individual points of dispute, for the return of fugitive apprentices, asking that justice might be done to aggrieved citizens, and on occasion threatening reprisal. Southampton had formal agreements with more than seventy towns or other trading bodies. During a period of twenty years the city authorities of London sent more than 300 letters on such matters to the officials of some 90 other towns in England and towns on the Continent. The merchants from any one town did not therefore trade or act entirely as separate individuals, but depended on the prestige of their town, or the support of the home authorities, or the privileges already agreed upon by treaty. The non-payment of a debt by a merchant of one town usually made any fellow-townsman liable to seizure where the debt was owed, until the debtor could be made to pay. In 1285, by a law of Edward I, this was prohibited as far as England was concerned, but a merchant from a French town might still have his person and property seized for a debt of which he may have had no previous knowledge. External trade was thus not so much individual, between some Englishmen and others; or international, between Englishmen and Frenchmen, Flemings, Spaniards, or Germans, as it was intermunicipal, as it has been well described. Citizens of various towns, London, Bristol, Venice, Ghent, Arras, or Lubeck, for instance, carried on their trade under the protection their city had obtained for them.