In this special programme, we bring together the ultimate rules of design - room by room. Across three series of The Great Interior Design Challenge, our designers have come up with cost-cutting, ingenious ideas about how to get a look for less, and they are all here.We also have some insider techniques for a better home used by our judges - Sophie Robinson and Daniel Hopwood - plus design secrets from the guest judges featured across the series - interior and architectural designer Oliver Heath, designer Orla Kiely and iconic interior designer Kelly Hoppen.We have broken down the home into five key rooms and compiled our very own step-by-step guide on how to make the most of each one of them. Meanwhile, presenter and architectural historian Tom Dyckhoff gives his own historic tour of the house - explaining how our homes have shaped up over the years.