King John, after the victory of Aljubarrota had firmly seated him on the throne, felt it necessary to give Portugal such an interval of peace after the great efforts of the Castilian wars, as King Diniz had given it after the cessation of the wars against the Moors. This peace was secured by a wise foreign policy, of which the key-notes were, a close alliance with England, and systematic non-interference with the affairs of Spain. He had seen the value of the assistance of England in the final throes of his struggle with Castile, and the English monarchs on their side felt the advantage of having such an ally as Portugal to act as a thorn in the side of Castile, should the Spaniards come to the help of the French. The statesmanlike idea of Henry II. of England when he supported the proposal of the Count of Flanders for the hand of the daughter of Affonso Henriques, that this marriage should cement an unwritten alliance of England, Flanders, and Portugal, against France, Scotland, and Castile, seems to have been in the minds of the English statesmen of the fourteenth and fifteenth centuries. Just as Scotland afforded a convenient base of operations, whether military or political, for France against England, so did Portugal give a similar position for the English to act from against Castile, and the subsequent history of Portugal shows how generously and wisely England treated her southern ally. The people of the two nations gladly supported the political ideas of their monarchs and rulers. Each country could supply what the other wanted. From Portugal, the English merchants could obtain fruits and wines, which found a ready market, and the Londoners, not satisfied with supplying the home demand only, distributed these products of the south among the countries of the north, and notably in those lying round the Baltic Sea, Sweden, Denmark, Pomerania, and Lithuania. On the other hand, the Portuguese had no manufactures, and gladly took in exchange for the productions of their fertile soil, the cloth not only of the English looms, but of those of Flanders, in which the London merchants dealt.
This alliance was maintained in spite of dynastic changes and political revolutions in the two countries. In 1389 the name of the King of Portugal was introduced into the Treaty of Paris as an ally of the King of England; in 1398 Richard II. sent a body of English archers, under Edmund Arnold of Dartmouth, to assist in repelling the incursion made into Portugal by the son of Ines de Castro and some Spanish knights; and in 1400 John I. recognized his brother-in-law, Henry of Lancaster, as Henry IV. of England, and was created by him a Knight of the Garter, being the first foreign sovereign to receive that honour. In 1403 Henry IV. solemnly ratified the Treaty of Windsor, and in the following year the illegitimate daughter of John I., by Ines Pires, was promised in marriage to Thomas, Earl of Arundel, one of the leaders of the English nobility. This marriage was regarded as a further bond of alliance, and was celebrated in 1405 in England with the greatest splendour. Equally friendly relations were maintained with Henry V. and with the rulers of England during the minority of Henry VI.; Henry V. sent provisions and troops for the expedition to Ceuta in 1415, and in 1428 a strong force of 144 lances was sent to join the King of Portugal. This English alliance was the key-note of the policy of John I., and it was maintained without a breach from the arrival of John of Gaunt in 1386 until the death of the great Portuguese monarch in 1433.
