1. A home location register (HLR) for a mobile communications system and adapted to provide subscriber information in response to received requests, the register comprising a plurality of query processors, data storage means one associated with each said query processor, an update processor for updating data stored in said storage means, a peripheral processor incorporating a local message switch and having means for receiving requests for subscriber transactions and for relaying each request via the switch to a said query processor, a transaction bus via which the query processors and the peripheral processor can communicate and via which said requests are routed, wherein each said query processor is associated with a respective group of system subscribers, wherein a set of data is associated with each said subscriber, said data comprising permanent data and temporary data, wherein each said data storage means comprises a first store containing the permanent data relating to all subscribers and a second store containing the temporary data relating to the group of subscribers associated with the query processor corresponding to that data storage means, wherein said received requests are allocated each to an available query processor on an essentially random basis, and wherein each said query processor has means for processing requests relating to subscribers in the group associated with that query processor and for forwarding requests relating to subscribers not in that group each to the respective query processor whose group contains the subscriber.