Kevin McCloud presents the first of four special programmes inspired by 15 years of Grand Designs. He begins with a look at the challenges of self-building in the city, where space is at a premium and architects have to be at their most ingenious. Kevin uses footage from the best urban builds from the show over the years, meets pioneers at the forefront of the latest architectural thinking and looks at clever innovations that continue to transform people's lives to reveal which designs work best and why.