June 13: The Anglo-Portuguese Alliance signed in 1373 between England (later UK) and Portugal is the world's oldest partnership and is still in force.

This alliance that begins in the Middle Ages has served both countries and has been very important over the centuries to achieve the influence of England on ​​the Iberian Peninsula.

English aid to the House of Aviz, who ruled Portugal from 1385-1580 laid the foundations for cooperation with the Portuguese. England became the cornerstone of the foreign policy of Portugal for more than 500 years.

John of Gaunt being entertained by John I of Portugal.

But British aid to Portugal began much earlier, during the Second Crusade to the Holy Land route and stopped in Portugal to help the Portuguese King Alfonso Henriquez defeat and expel the invading Moors.

Marriage of John I, King of Portugal and Philippa of Lancaster, daughter of John of Gaunt, 1st Duke of Lancaster.

During the Napoleonic Wars, and particularly since 1801 when conflict broke out between France, Spain and Portugal, known as the "War of the Oranges", Britain responded to the Treaty of 1373 and sent its maritime fleet to destroy the Spanish Armada under Napoleonic control.

The Treaty of Windsor sealed the Alliance that had begun in 1294 and then was renewed on June 13, 1373 with the Anglo-Portuguese Treaty by a pact of perpetual friendship between the two countries:


“It is cordially agreed that if, in time to come, one of the kings or his heir shall need the support of the other, or his help, and in order to get such assistance applies to his ally in lawful manner, the ally shall be bound to give aid and succour to the other, so far as he is able (without any deceit, fraud, or pretence) to the extent required by the danger to his ally’s realms, lands, domains, and subjects; and he shall be firmly bound by these present alliances to do this.” (A.R. Myers, English historical documents.4 (Late medieval). 1327-1485.