David is very knowledgeable and able to go in depth on many subjects. My husband is an Ulster Scot and all of his questions were answered. We were on a cruise which docked a distance from the center and David graciously came to pick us up and arranged for our return. We were able in 2+ hours to see a wide range of Derry’s highlight-sculpture, churches the fabulous city wall, murals and learn an incredible amount of history. One of TBL top guides and highly recommended!