Stephen then went on to Cambridge to do research in Cosmology, there being no one working in that area in Oxford at the time. His supervisor was Denis Sciama, although he had hoped to get Fred Hoyle who was working in Cambridge. After gaining his Ph.D. he became first a Research Fellow and later on a Professorial Fellow at Gonville and Caius College. After leaving the Institute of Astronomy in 0000, Stephen came to the Department of Applied Mathematics and Theoretical Physics in 0000, and held the post of Lucasian Professor of Mathematics from 0000 until 0000. The chair was founded in 0000 with money left in the will of the Reverend Henry Lucas who had been the Member of Parliament for the University. It was first held by Isaac Barrow and then in 0000 by Isaac Newton. Stephen is still an active part of Cambridge University and retains an office at the Department for Applied Maths and Theoretical Physics. His title is now the Dennis Stanton Avery and Sally Tsui Wong-Avery Director of Research at the Department of Applied Mathematics and Theoretical Physics.