Peace in their time

Despite the various civil and foreign wars that affected England in the 13th century, Michael Prestwich in English Politics in the Thirteenth Century (in the NU library) says those contemporaries who considered it, and especially Henry III's reign as a time of peace had some justification:

Not one [domestic?] political opponent of the crown was executed during the thirteenth century, a record not to be achieved again until the 19th century.

How can this success be explained? It was very important that men thought it was possible to achieve worthwhile ends by political rather than military ends...

The achievements were not the work of individuals alone: for all the imprecision of the concept, full credit must go to the community of the realm.

Image: Henry III's coronation.