Kevin McCloud meets Rupert and Julie Upton, who are building a very experimental idea in the Lambourn Valley. Their dream is to create an amazing cross-shaped house made of oak and glass, strikingly modern with the most superb views. But each piece of wood has to be custom made and the design itself is incredibly complex. Few people would have the courage to take on such an experimental build – will Rupert and Julie's bravery pay off?