England's trade, its war finance and its ability to bring force to bear against France were heavily reliant on seaborne transportation, especially to its territory in Gascony.

The English navy paralleled the march of the army, capturing or burning large numbers of French warships and merchant vessels as it went.

The Truce of Calais was agreed in September 1347[6] but the war continued via raids and guerrilla warfare;[7] the ongoing fighting was "almost constant".

Later in the year de la Cerda led a Castilian fleet of 47 ships loaded with Spanish wool from Corunna to Sluys, in Flanders, where it wintered.

In April it blockaded the English Channel ports, while the French struggled to reinforce it with what native ships they could finance and man.

[13] They were based out of Sluys, and several hundred Flemish adventurers joined their ranks, mostly equipped as crossbowmen, in the expectation of plunder.

Edward had good sources of intelligence in Flanders[15] and knew the composition of De la Cerda's fleet and when it sailed.

Edward was sitting on the deck of his ship, with his knights and nobles, listening to his minstrels playing German airs, and to the singing of young John Chandos.

When the look-outs in the tops reported the enemy in sight, Edward and his company drank to one another's health, the trumpet was sounded, and the whole line stood out.

There being no effective naval artillery at the time, battles at sea consisted of grappling with and boarding enemy vessels.

His son, Edward Prince of Wales, had a similar experience, his men reportedly barely fighting their way aboard their opponent before their own ship foundered.

At the close, the English vessel La Salle du Roi, carrying the king's household, and commanded by the Fleming Robert of Namur,[c] was grappled by a larger Castilian and was being dragged off.

A Flemish valet of Robert's, named Hannequin, boarded the enemy and cut the halliards of her mainsail with his sword, allowing other English ships to catch the Castilian, and it was taken.

Much of this action was visible from the English shore, and the clifftops near Winchelsea were lined with spectators, which gave the battle its name.

Trade with Gascony was less affected, but ships were forced to use ports in western England, often impractically far from their cargo's intended English markets.

[20] Others have suggested that the battle was just one of a number of significant and hard-fought naval encounters of the period, only recorded because of the prominent figures involved.

[25] With communications with Gascony now more secure, the English launched a large expedition from there in 1356 under the Prince of Wales, at the end of which the French suffered a devastating defeat.

[27] The main contemporaneous account for the battle is Jean Froissart, who was at different times in the service of Edward and of his wife, Philippa of Hainault, and of the counts of Namur.