The turbine bottleneck behind Commonwealth shipbuilding

Could Commonwealth shipyards have built more destroyers and cruisers before the Second World War?

Yes, but only if earlier investment also created the turbine plants, component supply, and skilled workforce needed to equip hulls.

Adding slipways in Canada or Australia would not by itself produce more destroyers or cruisers. Turbines, engines, and other complex components were a major limiting factor, especially when American capacity was committed to its own programmes. Starting large marine-turbine plants in the mid-1930s would give Commonwealth industry time to solve production problems before war arrived. The industrial lesson is that hull capacity and machinery capacity had to expand together.