A packet data network gateway, P-GW, is located in a second network for supporting user plane data to terminal devices in a wireless communications system that additionally comprises a first network having a first packet data network gateway, P-GW operably couplable to the P-GW. The P-GW comprises a processor arranged to: check a destination address of received packets from the first P-GW to determine whether the received packets are destined for any of the terminal devices, and in response thereto: extract one or more properties of said received packets if they are destined for any of the terminal devices served with user plane data; or discard said received packets if they are not destined for the terminal device(s).