He was regarded as one of the foremost book craftsmen and trade historians of modern times, lecturing and teaching in Europe (Belgium, Switzerland, and the Netherlands) and the Americas (Brazil, the United States, and Venezuela).
When he was sixteen, his father helped him secure a six-year apprenticeship at the British Museum Bindery, during which he was awarded the City and Guilds of London Institute's silver medal in Forwarding, the first prize.
At this time, he attended evening classes at the London School of Printing, and then secured the prestigious position of Craftsman-Demonstrator at the Royal College of Art, working under Roger Powell (who Middleton considered "one of the most important and influential bookbinders of the last hundred years and, arguably, of any period"[4]).
Also in 1951, he married Dora Mary Davies (d. 1997), an accountant who had formerly been in the WRAF — finding the work environment at Zaehnsdorf's untenable, the couple soon established their own book-restoration business in Soho.
[3][2] Around this time, Middleton was invited by the journal Paper & Print and the British & Colonial Printer to contribute a series of articles on historical or technical aspects of the craft, his topics of interest; he kept publishing many scholarly articles until 1958, when work on his A History of English Craft Bookbinding Technique began in earnest; his pioneering magnum opus was finally published in 1963, and was praised by the likes of Howard Nixon as "the first attempt to chart the history of English bookbinding in all its technical aspects", Carolyn Price Horton as "a chronology of the craft", and Roger Powell as "the door is here opened on a world that has heretofore been terra incognita to all but a very few bibliophiles and book collectors".
[5] That year, the British Library and Oak Knoll republished his memoirs (was first printed in 1995 by the Bird and Bull Press[1]), under the title Recollections: A Life in Bookbinding.