After the disasters that followed the collapse of Roman authority, trade, both international and internal, eventually grew, but its institutional infrastructure needed to be recreated. Even where towns eventually revived on old sites they operated with newly devised trading institutions and new monetary systems. During the eighth and earlier ninth centuries overseas commerce increased, especially through London, Southampton, Ipswich and York, and wider trading interests prompted currency reform as well as co-operation between the principal English monarchies. A single standard of currency established by the kings of Mercia and Wessex, together with the archbishop of Canterbury, implied a common interest in trade. But the later ninth and early tenth centuries experienced a temporary setback in parts of England as the Danish invasions of eastern England disrupted established institutions and practices. The level of international trade stagnated in the wics through which merchandise had previously passed, and the money supply diminished. Danish rulers ultimately proved no less interested than the English kings in fostering trade, but the coins they minted were of lower quality. No common standard of currency was re-established until King Edgar's new coinage of 973. The year 900 is accordingly a useful point at which to take stock of the institutional provision for trade, before proceeding to examine the subsequent revival of commerce in the Late Saxon and Anglo-Norman periods.