The third cause of the Dutch trading advantage was the English Civil War (1642–1651). From 1643 the English parliament began to embargo Dutch ships from trading with any ports in Great Britain in Royalist hands, which was matched later in the year by a corresponding Royalist embargo. Although few Dutch ships were seized by parliamentary forces for trading with the Royalists in 1643, the number seized rose from 1644 to 1646, causing considerable tensions: few Dutch ships were seized by the Royalists. Despite these provocative embargoes and their extension to Ireland and English colonies in Royalist hands, as late as 1649 the States General, and particularly the maritime provinces of Holland and Zeeland, wished to maintain their lucrative trade with England. Until 1648, Dutch naval vessels also inspected convoys of English ships which, as neutrals, were able to trade with the Spanish Netherlands. They sometimes brought ships into Dutch ports for more thorough examination and, very rarely, confiscated ships and cargoes as contraband.