British-born John Fletcher came to Australia in 1966 when he got a position as a Senior teaching Fellow at Monash University. In 1968 he was appointed to a lectureship in the Department of German at Sydney University as its first specialist in the German literature of the Baroque period. Fletcher was one of the world's foremost authorities on the 17the century German Jesuit Athanasius Kircher, on whom he had written his MA thesis, and throughout his life he kept researching connections between Germany and Australia.
Fletcher authored or edited about 20 books and bibliographies and wrote more than 30 articles and book chapters on bibliographic and literary matters. He took part in the setting up of the Christopher Brennan Society. As a committee member of the Friends of the Sydney University Library and, at times, its Treasurer, Secretary and, until his death, its President, he helped it raise thousands of dollars for books the library could otherwise not have afforded. He was long a member of the Book Collectors' Society of Australia and was at his death its President and Publications Editor.