A British atomic weapon available in the 1920s would have fallen outside the treaty system described in this counterfactual. Leaders would probably use it because its power would make contemporary strategic-bombing doctrine appear workable, unlike chemical weapons whose deterrent effect rested partly on the enemy possessing them too. The larger obstacle is the industrial and scientific system required to produce the bomb. A reactor programme, specialised machinery, and multiple supporting technologies would all have to mature together. Some of those foundations began in the 1910s without anyone knowing where they would lead. Even the wartime Manhattan Project was a close-run achievement, so moving the whole system two decades earlier requires much more than one premature discovery.
Notable Point · 2:12:37-2:14:26
Why an early atomic bomb needed an industrial ecosystem
A 1920s British atomic bomb would vindicate interwar bomber doctrine, but the reactor, machinery, and scientific foundations needed to build it were still decades from maturity.