Fleet and minelaying boats tested alternative submarine roles

The Royal Navy did not confine interwar submarine development to the main S, T, and U lines. River-class boats tested a submarine fast enough on the surface to accompany a fleet, a requirement most relevant to distant Pacific operations. Separate minelaying boats reflected British study of the damage German minelaying submarines had inflicted during the First World War. Both experiments generated design experience even though neither role became the dominant force structure. The quick progression from the O, P, and R boats to the T class also shows how little time a supposedly settled design remained current in a fast-moving technical field.