Flagship service led to wartime lessons at the Signal School

Promotion to commander did not send Somerville into a conventional executive post or destroyer command because the Navy still needed him on major flagships. In December 1917 he joined the Signal School as experienced specialists were brought back to Portsmouth to codify wireless, visual signaling, call signs, recognition systems, codes, and ciphers. Drawing those officers out of the fleet showed that the Royal Navy was already synthesizing the current war's lessons and preparing its communications system for a future conflict. Their subsidiary reports preserved operational evidence even when the main official account became politically contested. Signals material was damning about Battle Cruiser Fleet practices and remained available alongside the suppressed Jutland narrative.