International trade collapsed, and also became much less multilateral, during the 1930s. Previous studies, looking at aggregate trade flows, have argued that trade policies had relatively little to do with either phenomenon. Using a new dataset incorporating highly disaggregated information on the United Kingdom's imports and trade policies, we find that while conventional wisdom is correct regarding the impact of trade policy on the total value of British imports, discriminatory trade policies can explain the majority of Britain's shift toward Imperial imports in the 1930s.