An identification module for securely providing a mobile identity to a mobile data network for use in identifying mobile equipment in which that identification module is installed, the identification module comprising: a mobile identity storage controller for accessing a mobile identity memory (500, 540, 560) which securely stores data defining two or more different mobile identities; a selector for selecting a mobile identity from the two or more mobile identities; a network interface for generating data derived from the selected mobile identity for transmission to a mobile data network during a network authorisation procedure, and for receiving acknowledgement data back from the mobile data network indicating whether authorisation was successful based on that selected mobile identity; and a detector for detecting whether the acknowledgement data indicates an unsuccessful authorisation with the mobile data network and, if so, for initiating a further network authorisation procedure in which the selector selects a different one of the two or more mobile identities; the identification module further characterized in that: at least two of the mobile identities are temporary-use mobile identities which have been activated with the mobile data network; the identification module comprises a time controller for controlling use of the temporary-use mobile identities to no longer than a first predetermined trial period; the selector is configured to select a mobile identify from the two or more temporary-use mobile identities only during the first predetermined trial period; and the selector is configured to select only a single stored mobile identity, being specific to the identification module and not being one of the temporary-use mobile identities, and which requires a registration process, for use after the expiry of the first predetermined trial period, the selector being inhibited from selecting the single stored mobile identity during the first predetermined trial period. a mobile identity storage controller for accessing a mobile identity memory (500, 540, 560) which securely stores data defining two or more different mobile identities; a selector for selecting a mobile identity from the two or more mobile identities; a network interface for generating data derived from the selected mobile identity for transmission to a mobile data network during a network authorisation procedure, and for receiving acknowledgement data back from the mobile data network indicating whether authorisation was successful based on that selected mobile identity; and a detector for detecting whether the acknowledgement data indicates an unsuccessful authorisation with the mobile data network and, if so, for initiating a further network authorisation procedure in which the selector selects a different one of the two or more mobile identities; the identification module further characterized in that: at least two of the mobile identities are temporary-use mobile identities which have been activated with the mobile data network; the identification module comprises a time controller for controlling use of the temporary-use mobile identities to no longer than a first predetermined trial period; the selector is configured to select a mobile identify from the two or more temporary-use mobile identities only during the first predetermined trial period; and the selector is configured to select only a single stored mobile identity, being specific to the identification module and not being one of the temporary-use mobile identities, and which requires a registration process, for use after the expiry of the first predetermined trial period, the selector being inhibited from selecting the single stored mobile identity during the first predetermined trial period.