 Hartley spent a year at the University of Chicago, and another at MIT before being appointed as a lecturer at the newly established University of Warwick in 1966, and was promoted to reader in 1973.He moved to a chair at School of Mathematics at the University of Manchester in 1977 where he served as head of the Mathematics department between 1982 and 1984.He published more than 100 papers, mostly on group theory, and collaborated widely with other mathematicians.