For generations a family of Somerset farmers have been wondering if there was ever actually a castle on top of the hill they call Castle Hill. A medieval charter refers to a Norman castle in the area, but they are not clear about exactly where and there are several likely locations. Geophysics' radar shows a large rectangular structure, possibly a keep. There is debate as to whether it was timber or stone. Raksha and Paul are excited by some 12th century pottery, indicating that the building may date from the Anarchy period rather than the Norman conquest. Moreover, a metal spur hints at a cavalry based fort. They are joined by castles expert Marc Morris, and quarryman Zak England demonstrates how to split a stone. Phil tastes mead for the first time. Mick is beginning to doubt whether the building was ever completed.

• Tim Taylor

• Tony Robinson
• Bill Oddie
• Phil Harding