Although Portugal has a small size is still amongst the 10 largest wine producers in the world. Abroad probably the best known Portuguese wines are the Port and Madeira wines. Both of them are fortified wines and were invented by accident. In the 17th and 18th centuries often wines were shipped for long distances and brandy was added as a preservative. Certainly the alliance made by Portugal and Britain through the Treaty of Windsor in 1386 was a starting point for the arrival of British that settled in Portugal as early as the 15th century. By the 18th century Port and Madeira wines were leading Portuguese exports.