1. A geolocation data storage system for communication session data from a mobile radio communications network, the mobile radio communications network supporting mobile communication units, the geolocation data storage system comprising: a first storage area, the first storage area operable to store a record of data for each communication session taking place in at least one geographical region of the mobile radio communications network; a first processing module, the first processing module operable to access the stored record of data for a communication session, to identify a subset of the data for the communication session, and to derive geo-location information; and a second storage area, the second storage area operable to store the subset of the data for the communication session, and the geolocation information for the communication session.