This chapter outlines the plan which Leslie Martin and his associates submitted to Charles Pannell in 1965, reviewing what Whitehall’s architecture of ‘better times and more spacious days’ would have been like. ‘Better’, in this instance, was imagined to mean modern, functionally optimised and designed to accommodate quickening change. ‘More spacious’ did not just mean less cramped oces for civil servants but also new arcades, river-front balconies, parks and pedestrian spaces for the public. The proposals were imagined as a consistent vision, a ‘total plan’ where the most ecient space-use, building mass, building population, oce depth and daylighting were quantied and calculated. These technical priorities reected the architects’ academic interests in reconciling science with art in architecture. They also reected the purposeful aspirations of that distinctive time, loosely labelled White Heat, when many politicians and professionals considered themselves to be engaged in active planning towards the rapid achievement of a new computer age.