For the first time in a while I was contacted by a Gammon with ancestors from North Devon like mine. Malcom now lives in Western Australia, and sent me some brief information that he knew about his family.
I have pulled together a tree from this information and published it on my Drupal website:
Malcom’s grandfather is Stanley A GAMMON. Stanley married Ivy M PARKIN in Barnstaple in 1921 (Sep 1921, Barnstaple, Vol: 5b, Page: 1073). A copy of this marriage certificate would confirm Stanley’s parents. In any case, I should be able to find Stanley in the 1911 census.