Following the defeat of Spain in the war, England meditated the Treaty of Lisbon in 1668 which saw the independence of Portugal and the recognition of Pedro II as King.The English alliance was decisive in the consolidation of the independence of Portugal, and in Pedro's leadership.England's support for Portugal during their Restoration War was confirmation of the renewal of the alliance.
Philippa provided royal patronage for English commercial interests that sought to meet the Portuguese desire for cod and cloth in return for wine, cork, salt, and oil shipped through the English warehouses at Porto.
Her eldest son, Duarte, authored moral works and became king in 1433; Pedro, who travelled widely and had an interest in history, became regent (1439-1448) after Duarte died of the plague in 1438; Ferdinand the Saint Prince (1402-1443), who became a crusader, participated in the attack on Tangiers in 1437; and Henrique – also known as Prince Henry the Navigator (1394-1460) – became the master of the Order of Christ and the instigator and organiser of Portugal's early voyages of discovery.
The Anglo-Portuguese Alliance (or Aliança Luso-Britânica, "Luso-British Alliance", also known in Portugal as Aliança Inglesa, "English Alliance"), ratified at the Treaty of Windsor in 1386, between England (succeeded by the United Kingdom) and Portugal, may be the oldest alliance in the world that is still in force – with the earliest treaty dating back to the Anglo-Portuguese Treaty of 1373 – although this claim is disputed by some historians who believe the Auld Alliance between Scotland and France, first signed in 1295, may still be in effect.
Historically, the Kingdom of Portugal and the Kingdom of England, and later the modern Portugal and United Kingdom, have never waged war against each other nor have they participated in wars on opposite sides as independent states since the signing of the Treaty of Windsor.
The Iberian Union (1580–1640), a 60-year dynastic union between Portugal and Spain, interrupted the alliance.
The struggle of Elizabeth I of England against Philip II of Spain in the sixteenth century meant that Portugal and England were on opposite sides of the Anglo-Spanish War (1585–1604) and the Dutch–Portuguese War.Portuguese foreign policy became tied to Spanish hostility to England.However in 1640 England supported the Portuguese House of Braganza to take power in Portugal replacing the House of Habsburg, putting an end to a 60-year dynastic union between Portugal and Spain.The most important part of the treaty stated that: 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.In July 1386, John of Gaunt, Duke of Lancaster, son of the late king Edward III of England and father of the future King Henry IV of England, landed in Galicia with an expeditionary force to press his claim to the Crown of Castile with Portuguese aid.However, English aid to Portugal went back much further to the 1147 Siege of Lisbon, when English and other northern European crusaders – en route to the Holy Land to participate in the Second Crusade – stopped and helped Portuguese King Afonso Henriques to conquer the city from the Moors.