1. A computer-implemented method of controlling asynchronous installation of a software update on a terminal device of a plurality of terminal devices on a wireless network, the method comprising steps of: at an application gateway mediating between the plurality of terminal devices and an online profiles registry, the online profiles registry containing information identifying applications installed on each of the plurality of terminal devices, the application gateway including a processor: receiving, at the application gateway, an update notification message in respect of the software update, the update notification message comprising: a software identifier uniquely identifying an application affected by the update; a version number associated with the software update; and an address of an update script on a data network accessible by the terminal device, the update script being adapted to install the software update on the terminal device; based on the software identifier, searching, using the application gateway, the online profiles registry to identify terminal devices on which the application identified by the software identifier is installed; and forwarding, from the application gateway, a notification message to the identified terminal devices, the notification message including the software identifier, the version number and the address of the update script, wherein the profiles registry comprises a plurality of profiles, each profile being associated with a respective terminal device and containing, for each application installed on the respective terminal device, the respective software identifier of the application, and a current version number indicative of a version of the installed application, and wherein the step of searching the profiles registry comprises a step of identifying each terminal device for which the software identifier of the update matches that of an application installed on the terminal device.