Abstract: A user device comprises a user interface, a wireless transceiver having a local wireless communication range, computer storage and a processor. The computer storage is configured to store a messaging application for effecting a secure messaging session via a network between the user device and at least one remote device. The messaging application comprises a locking component for locking the secure messaging session. The processor is configured to execute the messaging application. The locking component of the messaging application is configured to determine in response to an unlock input received via the user interface whether a trusted device is present within the local wireless communication range, and to unlock the secure messaging session in dependence thereon.