Henry's son Jim Clay was a prototype for Jim Brading.
According to Christina Hardyment Henry Clay had four children; Gabriel, Jim, Helen and John. Jim was going to Oxford when he met Ransome in 1935, though Jim Clay himself thought that Jim Brading was a mixture, also owing something to Dick Tizard. The Clay yacht Firefly was very like the Nancy Blackett, and Ransome was impressed to hear that on a voyage to Holland and back the four children took charge (an inspiration for WD?).
We Didn’t Mean to Go to Sea is dedicated To Mrs. Henry Clay