ISANNAVATIA in Britain, mentioned in the 6th Itinerary as lying between Lactodurum and Tripontium. It is a name of some difficulty, since neither of the places on each side of it has been identified. (See vv.) In the Geographer of Ravenna we find a Bannovallum, and in the 8th Itinerary a Bannovantum. Probably these two names are identical. At any rate, Bannovantum == Isannavatia, since each is 28 miles from Magiovinium. Thus, in the 6th Itinerary, we have:— MagiovinioM. P. Lactodoroxvi. Isannavatiaxii=-xxviii.And in the 8th:—M. P. Bannavanto Magiovinioxxviii.
It is only safe to say that Isannavatia was a town in the southern part of Northamptonshire, probably Daventry. The Itinerary in which it occurs has only two names beyond doubt, viz. Verulamium and Lindum ( St. Alban's and Lincoln). Daventry, however, is Horsley's identification. In more than one map of Roman Britain, Bannovallum is placed in Lincolnshire. This is because it is, in the first place, separated from Bannovantum, and then fixed on the river Bain, a Lincolnshire river. This is the meaning of Horncastlebeing given as its equivalent. The change, however, and the assumption, are equally gratuitous.
[R.G.L]