In the nineteenth century socialists wanted to abolish rule by private economic interest, but the idea of the planned economy to replace capitalism was born only in the twentieth. The birth of the concept of planning was thus a seminal event, both for economic theory and perhaps still more importantly for socialism. Attempts to devise and implement schemes for the central direction of nations' economic lives in supersession of private enterprise marked a step away from mere utopianism; and, somewhat paradoxically, such planning was also a major departure from marxian anti-utopianism, which saw attempts to describe the future socialist order as futile, given that such an order was bound inevitably to evolve as a product of historical forces. The planned economy as a practical phenomenon found expression in Germany during World War I, an example followed consciously by the Russian Bolsheviks after 1917; British state intervention in the economy during war time had far less long-term impact on the theory and practice of socialism. This chapter cannot, of course, give a comprehensive description of all these complex practical and theoretical developments. Rather, its purpose is simply to explore their relative impact upon the British labour movement in the years before 1931, with a view to establishing that year as a turning point in Labour's economic thought. Therefore, a consideration of the domestic and European intellectual traditions which in time contributed to the British ‘planning boom’ of the thirties will take place in parallel with a discussion of the relevant practical questions of Labour politics.