When "Sydney" did not arrive on schedule, there was no immediate concern: the northbound journey with "Zealandia" could have taken longer than expected, "Durban" could have been late to the rendezvous, "Sydney" could have diverted to aid southbound merchant shipping, or minor engine problems could have occurred. Warships were expected to maintain wireless silence unless absolutely necessary; none of these were sufficient reason to break silence and inform Fremantle of the delay. When the ship failed to arrive by 23 November, wireless communications stations (initially those in Fremantle, then all high-power stations in Australia) began signalling ordering "Sydney" to report in.