This is quite the catch Mr. Ritchford. In fact, it was not just the Last theorem, but there were multitudes of others, too for which Fermat wrote the same thing over and over on the margins of the book, while sometimes the excuse was that he had to feed his cat and sometimes it was because he had to water the garden. Though we will never know his mathematical aspect, but his scribbles are quite something to discuss for math enthusiasts like you and me!