A method in a cellular telecommunications network, the cellular telecommunications network including a central base station unit, a first donor base station and a distributed base station unit, the central base station unit having a first interface for communicating with a first cellular core networking node and a second interface for communicating with the first donor base station, the first donor base station having a first interface for communicating with the central base station unit and a second interface for wirelessly communicating with the distributed base station unit, the distributed base station unit being mobile and having a first interface for wirelessly communicating with the first donor base station and a second interface for communicating with a User Equipment, UE, wherein the UE's user traffic is transmitted between the central base station unit and the UE via the first donor base station and the distributed base station unit, wherein there is a first connection between the central base station unit and the distributed base station unit via the first donor base station, wherein the central base station unit and distributed base station unit implement a first functional split in which a first set of protocol functions are implemented in the distributed base station unit and a second set of protocol functions are implemented in the central base station unit, the method comprising the steps of: discovering a second donor base station having a first interface for communicating with the first central base station unit and a second interface for wirelessly communicating with the distributed base station unit; determining a capacity of a second connection between the central base station unit and the distributed base station unit via the second donor base station; determining that the capacity of the second connection is either more of less than a capacity of the first connection; and, in response to this determination, causing the centralised base station unit and the distributed base station unit to implement a second functional split in which a third set of protocol functions are implemented in the distributed base station unit, the third set of protocol functions including fewer functions than the first set of protocol functions if the capacity of the second connection is more than the capacity of the first connection or including more functions than the first set of protocol functions if the capacity of the second connection is less than the capacity of the first connection, and a fourth set of protocol functions are implemented in the central base station unit, the fourth set of protocol functions including more functions than the second set of protocol functions if the capacity of the second connection is more than the capacity of the first connection or including fewer functions than the second set of protocol functions if the capacity of the second connection is less than the capacity of the first connection; and initiating a handover of the distributed base station unit from the first donor base station to the second donor base station. discovering a second donor base station having a first interface for communicating with the first central base station unit and a second interface for wirelessly communicating with the distributed base station unit; determining a capacity of a second connection between the central base station unit and the distributed base station unit via the second donor base station; determining that the capacity of the second connection is either more of less than a capacity of the first connection; and, in response to this determination, causing the centralised base station unit and the distributed base station unit to implement a second functional split in which a third set of protocol functions are implemented in the distributed base station unit, the third set of protocol functions including fewer functions than the first set of protocol functions if the capacity of the second connection is more than the capacity of the first connection or including more functions than the first set of protocol functions if the capacity of the second connection is less than the capacity of the first connection, and a fourth set of protocol functions are implemented in the central base station unit, the fourth set of protocol functions including more functions than the second set of protocol functions if the capacity of the second connection is more than the capacity of the first connection or including fewer functions than the second set of protocol functions if the capacity of the second connection is less than the capacity of the first connection; and initiating a handover of the distributed base station unit from the first donor base station to the second donor base station.