Apparatus and a corresponding method of operating a hub device, and a target device, in a coherent interconnect system are presented. A cache pre-population request of a set of coherency protocol transactions in the system is received from a requesting master device specifying at least one data item and the hub device responds by cause a cache pre-population trigger of the set of coherency protocol transactions specifying the at least one data item to be transmitted to a target device. This trigger can cause the target device to request that the specified at least one data item is retrieved and brought into cache. Since the target device can therefore decide whether to respond to the trigger or not, it does not receive cached data unsolicited, simplifying its configuration, whilst still allowing some data to be pre-cached.