He has held a number of curating and academic posts in art history in the United Kingdom and researched and written extensively on medieval religious images in a variety of media, including stained glass and illuminated manuscripts.
[4] An academic career beckoned in 1992 when he was appointed to a personal chair in the History of Art Department at the University of York as Professor in Medieval Stained Glass, a post he held until 2008.
[11] Marks has also been active with the Corpus Vitrearum Medii Aevi project, serving as its International President and contributing to its list of Summary Catalogues of medieval stained glass in the counties of Northamptonshire and Bedfordshire and Buckinghamshire.
[12] Mark's scholarship and experience were in evidence when he was approached by the Victoria and Albert Museum (V&A) to contribute to a future exhibition that was in its very early planning stages in the 1990s.
Writing in 2003 in the V&A Conservation Journal, Paul Williamson, then Keeper of Sculpture, Metalwork, Ceramics & Glass at the museum, describes how Marks came to be a key figure in the exhibition 'Art of England 1400-1547' held at the V&A in 2003.
[15] The collection, which includes film and glass negatives as well as prints, consists mainly of architectural and sculptural images and holds the archives of Paul Laib and Anthony Kersting.