A roaming home location server is arranged to receive signalling data communicated between a home location server of a first home mobile radio network and a visitor location server of a second visited mobile network. The signalling data is associated with informing the home location server of the location of a mobile user equipment which has roamed from the first home mobile radio network to the second visited mobile network. The signalling data received by the roaming home location server from the visitor location server of the second visited mobile network includes a request to register the roaming mobile user equipment with the visitor location server of the first visited mobile network. The roaming home location server is arranged to register the roaming user equipment with the visitor location server of the first visited mobile network and to communicate the request signalling data to the home location server of the second home mobile radio network, and in response to rejection signalling data representing a rejection of the request to register the roaming mobile user equipment with the visitor location server of the first visited mobile network, to generate further request signalling data which has an effect of causing the home location server of the first home network to accept the registration of the roaming mobile user equipment with the visitor location register of the first visited mobile radio network.