Architect George Clarke returns for a seventh series. George and master craftsman Will Hardie travel around the UK visiting ingenious and eccentric builds created by pioneering small space designers. From abandoned sewage works and subterranean air raid shelters, even cockpits of commercial airplanes and cattle trucks, the series shows how a bit of vision and innovative design can transform even the most unusual space into a thing of beauty. George travels to Japan, where innovation and ground-breaking design blend seamlessly to create breath-taking spaces like no other. And the boys attempt the impossible: to build their own four-tonne toy tree house.