Common name (also British Association House) for a historically important building in the Gregorian style in the Portuguese port city of Porto. It was occupied in 1790 by British port wine trading houses under Consul John Whitehead (a predecessor building built as early as 1727 stood elsewhere). It is the only surviving "factor's house" where "factors" (trade commissioners) once negotiated and concluded their deals on foreign territory. The British wine merchants who met regularly in the Factor House had a decisive influence on the port wine business. The foundation stone for the port wine boom was laid by the treaty concluded as early as 1703 and known as the Methuen Treaty, which provided for special customs concessions for the import of Portuguese wines in England. As a result, the British gained an absolute monopoly on the port wine trade.