A method of authenticating User Equipment (UE) to a wireless telecommunications network, wherein the UE is subscribed to a first wireless telecommunications network, and authenticating being performed so as to subscribe the UE to a second wireless telecommunications network, and wherein there is an absence of a roaming capability between the first wireless telecommunications network and the second wireless telecommunications network for the UE, the method including generating, at the first wireless telecommunications network, a network key for authenticating the UE at the second wireless telecommunications network; loading the generated network key to the second wireless telecommunications network; subsequently communicating the generated network key to the UE from the first wireless telecommunications network; and authenticating the UE at the second wireless telecommunications network by communicating the network key from the UE to the second wireless telecommunications network, thereby to permit the UE to subscribe to the second wireless telecommunications network.