The difficulty of the manoeuvre is attested to by the King's own ship, the "Cog Thomas", striking the Castilian it was attempting to grapple so heavily as to spring English ship's timbers. At the second attempt, it successfully grappled and archers deterred Castilians attempting to drop large rocks from their higher deck. The Castilian ships towered above the diminutive English ones; "like castles to cottages" as a contemporary wrote. Using scaling ladders the English men at arms boarded the Castilian ship and cleared its deck. Edward transferred his flag, as "Cog Thomas" was clearly sinking. 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. Their assault was aided by Henry of Lancaster attacking from the other side. La Cerda's crossbowmen caused many English casualties, firing from their elevated positions as the English closed and then attempted to board. The higher-built and heavier Castilian vessels were able to drop bars of iron or other weights on the lighter English vessels, causing serious damage. The conflict continued until twilight. At the close, the English vessel "La Salle du Roi", carrying the king's household, and commanded by the Fleming Robert of Namur, 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.