Teachers appear to own it, just allowing perpetual non exclusive rights to university: www.admin.cam.ac.uk/univ/so/pdfs/2022/ordinance13.pdf
30. In relation to teaching materials prepared by a University staff member for use in the teaching primarily of the University’s students, unless the Faculty Board or other body responsible for teaching has agreed explicitly to the contrary, the University shall have a non-exclusive, royalty-free, perpetual licence to use the material for teaching in the University.