A telecommunications system is disclosed, including a first radio access technology (legacy: GSM; UMTS/UTRAN) having a first radio access network (node B 15, RNC 17), and a second radio access technology (EUTRA) having a second radio access network (AP 20), wherein said first radio access network (node B 15, RNC 17) is divided into a plurality of first areas and said second radio access network (AP 20) is divided into a plurality of second areas, and wherein a home subscriber server entity (HSS 10) is provided that is common to both the first and second radio access technologies (legacy: GSM; UMTS) and which controls in which of the first and second areas a mobile terminal (UE 1) is registered, characterized in that a common control plane gateway entity (CP-GW 24) is provided through which communications from the first and second radio access networks, which relate to the first and second area which the mobile terminal (UE 1) occupies, are routed.