My understanding is that, until fairly recently, recitation of the English alphabet was often suffixed by saying "and per se and", roughly translating to "and, by itself, '&'". This suggests that the ampersand was almost sort-of a letter in the English alphabet -- this seems strange to me, because that would make it the only letter which represents an entire word (Latin 'et', meaning 'and') rather than a phonetic sound.
Was the ampersand considered a full citizen of the original Latin alphabet, and, if so, did it evolve into some vestigial afterthought in the modern English language? If so, were there originally other Latin letters that represented full words rather than phonetic sounds?