Complex sentence: Letocetum ceased to be used by the military after about 130, leaving the town probably under the authority of the civitas of the Cornovii with its capital at Viroconium Cornoviorum.
Split into simpler sentences: Letocetum ceased to be used by the military after about 130, the town was then under the control of the civil authority. The authority was probably the civitas of the Cornovii with its capital at Viroconium Cornoviorum.