A method of managing identities for use in a mobile telecommunications device in a telecommunications network, the method comprising: triggering an identity management process in a subscriber identity module of the mobile telecommunications device connected to a mobile telecommunications network, wherein each step of the identity management process is performed within the subscriber identity module; detecting at the mobile telecommunications device one or more parameters associated with the mobile telecommunications device; in the identity management process performed within the subscriber identity module, selecting an identity management rule to prioritise identities for use as an active identity for the mobile telecommunications device, wherein the identity management rule selected is determined by the one or more parameters detected; in the identity management process performed within the subscriber identity module, searching an identity database in the mobile telecommunications device wherein each record comprises an identity stored in the subscriber identity module and additional identity information for each identity, wherein the searching prioritises records according to the identity management rule; in the identity management process performed within the subscriber identity module, selecting a selected identity when a record conforming to the identity management rule is found in said searching; and in the identity management process performed within the subscriber identity module, modifying (4, 5) an active identity of the mobile telecommunications device to be the selected identity when the active identity is not already the selected identity. triggering an identity management process in a subscriber identity module of the mobile telecommunications device connected to a mobile telecommunications network, wherein each step of the identity management process is performed within the subscriber identity module; detecting at the mobile telecommunications device one or more parameters associated with the mobile telecommunications device; in the identity management process performed within the subscriber identity module, selecting an identity management rule to prioritise identities for use as an active identity for the mobile telecommunications device, wherein the identity management rule selected is determined by the one or more parameters detected; in the identity management process performed within the subscriber identity module, searching an identity database in the mobile telecommunications device wherein each record comprises an identity stored in the subscriber identity module and additional identity information for each identity, wherein the searching prioritises records according to the identity management rule; in the identity management process performed within the subscriber identity module, selecting a selected identity when a record conforming to the identity management rule is found in said searching; and in the identity management process performed within the subscriber identity module, modifying (4, 5) an active identity of the mobile telecommunications device to be the selected identity when the active identity is not already the selected identity.