Note 135
Paul Warnefrid (de Gestis Langobard. 1. iv. c. 44, p. 853, edit. Grot.) allows that Arianism still prevailed under the reign of Rotharis (A.D, 636-652). The pious Deacon does not attempt to mark the precise era of the national conversion, which was accomplished, however, before the end of the seventh century.
The History Of The Decline and Fall Of The Roman EmpireVolume 1Chapter 37