This book has put forward an explanation of how it was that the dukes of the Normans came to take and then hold the territory that became known as Normandy from the 1020s and won and maintained the fidelity of the lords and lesser men living on it.

To dominate their neighbours and to turn at least some of them into their subjects, as well as to gain a degree of control over them, the dukes needed wealth – or at least the promise of it – and a good reputation for leadership, success in war, generosity, and justice. These attributes attracted warriors and others seeking to make a career through service to a lord. Thus, or so it may be supposed, Rollo had demonstrated his right to rule those Vikings who had come with him to Francia. His successes ensured that his warriors remained with him, his leadership saw Rouen fall to him, and the reputation he gained as a result of his successes, military, diplomatic, and economic, brought King Charles to the negotiating table, so that c. 911 he legitimized Rollo's de facto possession of Rouen by granting it to him along with the surrounding district.

King Charles's grant c. 911, as well as the grants of 924 and 933 did not mean that the dukes immediately gained power over the whole of the territory concerned. They did not map out a ready-made territory of Normandy. Equally, the establishment over ducal power across what would come to be Normandy did not follow a smooth trajectory. There were defeats and reverses. The assassination of William Longsword threw the future of Rollo's line into doubt. It seems that Rouen was almost lost to the Franks, just three years or so after the Loire Vikings had lost Nantes to the Bretons. Indeed, it is possible that the Vikings of the Seine only retained their hold on Rouen because the remaining Vikings of the Loire, who had perhaps taken shelter in the Cotentin and Bessin, could come to their aid. But even though the Normans survived the turmoil of the period between 942 and 945, still Richard I had to survive the attacks of King Lothair and Count Theobald of Chartres.