Two historic stone wall specialists will be talking at the upcoming UPSURGE Festival in the Bay of Islands. Kate Ballard's book Stone Wall Country: The Dry Stone Walls of Bay of Islands and Kaikohe was based on interviews with local residents, including direct descendants of the original wall builders. At her talk "Stories behind walls" she'll be joined by fellow enthusiast Bill Edwards, Heritage New Zealand's area manager. There are hundreds of kilometres of dry stone walls, made from volcanic rocks in the region, so they're an important part of the landscape. Lynn Freeman talks with Kate and Bill, and first asks how these walls were built. Kate Ballard and Bill Edwards' "Stories behind walls" takes place on Saturday 24 Sept at the Plough & Feather in Kerikeri. It's part of Upsurge the Bay of Islands Arts Festival.