While Portugal was subsumed under the Iberian Union, rebellious Portuguese factions and government in exile sought refuge and help in England.

[3]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.

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.

England, in addition to military support on the ground, would protect Portuguese shipments in the Mediterranean and the coasts of Lisbon and Porto.

Following the defeat of Spain in the war, England mediated the Treaty of Lisbon in 1668 which saw the independence of Portugal and the recognition of Pedro II as King.

In return Portugal promised to transfer to the English the majority of the places recovered from the Dutch, to share in half the commerce of cinnamon and to install English families with the same privileges as Portuguese families in Goa, Cochin, Diu, Bahia, Pernambuco and Rio de Janeiro.

"Immortal trophies George's throne surround:Here Envy crush'd, and there Ambition boundBraganza's line by Gratitude combin'dClears fast to Brunswick's ever closely twin'd.

"The alliance was reconfirmed after the breakup of the Iberian Union, primarily due to both countries' respective rivalries with Spain, the Netherlands, and France, both in Europe and overseas.