The Gascon wine trade sustained English sea power

Early-fourteenth-century figures put Bordeaux's wine exports at more than 80,000 tons, with at least a thousand ships clearing the port each year. Duties on the wine could equal or exceed the customs revenue of England, while Gascony made a net contribution of £13,000 to the English Exchequer in 1324. The wine economy expanded as the territory available for food production contracted, making imported grain, fish, and other supplies essential. Convoy disruption therefore threatened famine in Gascony as well as financial disaster for the English crown. Bayonne's shipowners handled much of this traffic and supplied vessels and skilled mariners to English service. Gascony also connected Atlantic shipping with routes around Iberia and into the Mediterranean. Merchant shipping, port capacity, and convoy security formed the practical foundation of medieval English sea power.