In the winter, the island becomes Spitzbergen: Titty says ‘"It's Spitzbergen ... just for now, but you can see what a splendid place it is when it’s Wild Cat Island" (WH13).
Wild Cat Island appears to be a combination of several actual islands in both Coniston Water and Windermere. Peel Island is the location of the Secret Harbour and also has a small campground and rocky edges. Ransome wrote that he had taken features from Peel Island and Blakeholme on Windermere. He also suggested that Ramp Holme had contributed features to his composite island.
He wrote in his Autobiography of a trip with the Collingwood girls to: Peel Island, the island that had mattered so much to me as a small boy, was in the distant future to play its part in some of my books, and is still, in my old age, a crystallising point for happy memories.