Between 1266 and about 1305, messengers flew almost ceaselessly between the royal court at Paris and the royal court in Naples. Sometimes the two courts were in complete harmony; more often there were minor strains between them; only occasionally (as in 1303, when Charles II solidly backed Boniface VIII after Anagni) did a temporary breach occur. But even then, there was cause for negotiation, for an attempt to pour oil on troubled waters. For almost the whole of the reign of Philippe III (1270–85), contact was regular; and although Philippe IV (1285–1314) was less closely involved in the fate of the Regno than his father, and his own interests coincided less easily with those of Charles II than his father's had with Charles I's, there were still many urgent matters to be discussed between them. So in Paris, major events in the Regno were regularly commented on, as is attested in the chronicle of the Saint-Denis monk Guillaume de Nangis.

Charles of Anjou's conquest of the Regno would not have been possible without the consent and active support of Louis IX (1228–70) of France. There have been those who thought it was given reluctantly; but few modern historians follow this line. By the time Charles set off in 1265, Louis was convinced that the Regno must be in safe hands before Outremer could be given the help it so desperately needed.