A telecommunications system is arranged to provide a mobile communications session to a mobile node using an internet protocol. The telecommunications system comprises a home packet data network which includes a home agent of the mobile node and a visited packet data network. One of the home packet data network or the visited packet data network includes a packet data gateway for controlling the communication of the internet packets to and from the home packet data network from and to the visited packet data network. The mobile node is arranged to communicate a correspondent node binding update internet packet to the correspondent node via the packet date gateway, when the mobile node changes affiliation from the home packet data network to the visited packet data network. The correspondent node binding update internet packet provides a care of address of the mobile node within the visited packet data network and a home address of the mobile node. The packet data network is arranged to store the home address of the mobile node in association with the care of address of the mobile node, to adapt the correspondent node binding update internet packet by replacing the care of address in the received correspondent binding update packet with the address of the packet data gateway, and to communicate the adapted correspondent binding update packet to the correspondent node. The correspondent node therefore receives a correspondent binding update with the packet data gateway as the care of address. Thus, when the correspondent node communicates with the mobile node using the care of address of the packet data gateway, the packet data gateway can adapt the received internet packets, replacing the packet data gateway's address as the destination address with the care of address of the mobile node. Therefore, although a route optimisation process has taken place the internet packets are still routed via the packet data gateway .