Gregory read Mathematics at the University of Cambridge, specialising in applied mathematics and fluid dynamics. He was awarded a BA in 1984 and a PhD in 1990 (working on heat flow and air movement in buildings). He remained in Cambridge University, with a research fellowship from NERC working on the structure of buoyant jets and plumes. From 1991 - 1999 he was a Royal Society University Research Fellow at the School of Ocean and Earth Science (formerly Department of Oceanography), Southampton Oceanography Centre, University of Southampton; where he worked on flow through straits and density currents. Gregory joined UMIST in January 2000.