ISU´RIUM in Britain, first mentioned by Ptolemy (Ptol. 2.3.16) as a town of the Brigantes. It then occurs in two of the Itineraries, the 1st and 2nd. In each, it lies between Cataractonium and Eboracum ( Catterick Bridgeand York). Isubrigantum, in the 5th Itinerary, does the same.
In the time of the Saxons Isurium had already taken the name of Eald-burg( Old Towns) out of which has come the present name Aldbosrough, near Boroughbridge, with which it is undoubtedly identifled.
Roman remains, both within and without the walls, are abundant and considerable at Aldborough;the Stodhart (or Studforth), the Red Hill, and the Borough Hill, being the chief localities. Tesselated pavements, the foundations of large and spacious buildings, ornaments, implements, Samian ware, and coins with the names of nearly all the emperors from Vespasian to Constantine, have given to Isurium an importance equal to that of York, Cirencester, and. other towns of Roman importance.
[R.G.L]