Interested in the heritage of the area, Nicholas joined the Cumberland and Westmorland Antiquarian and Archaeological Society in 1927. Intrigued by the possible connection between Buttermere and the Norse landowner Bueth, mentioned in official documents relating to Cumberland at the time of the Norman conquest in the early 12th century, he produced a booklet, The Epic of Buttermere portraying the secluded valley as a stronghold of resistance to the invaders, and site of a supposed Battle of Rannerdale Knotts. This was so successful that in 1929 he wrote an expanded and illustrated novella version, The Secret Valley. This too was a great success, and in 1930 Frederick Warne, publisher of the Beatrix Potter books produced a new edition.