Ben and Rachel Hammond have spent a year searching London for somewhere exciting to live with their two daughters, and they have finally stumbled on a 1950s home on a unique plot, situated within the leafy depths of a park in the south of the city. The only problem is the house itself - an ugly, inefficient and uninspiring property - and their solution is to radically redesign it into a sleek, modernist masterpiece. But this is no easy task, as Kevin McCloud finds out.