William James came to the Department of Biochemistry at Oxford as a graduate student, having done a first degree in genetics at Birmingham, and completed a DPhil in microbiology with Joel Mandelstam.

In 1984 he was appointed to a departmental demonstratorship (junior lecturership) in bacteriology in the Dunn School. He has remained in the department ever since, rising to the position of Professor of Virology in 2006. His research focus shifted from bacterial genetics to HIV, and the routes by which the virus evades the defences of the immune cells that it infects. Technologies he has applied in his research include RNA interference and embryonic stem cells, and in 2008 he co-founded the Oxford Stem Cell Institute.

Alongside his research James has played a key role in the administration of the Dunn School, overseeing the finances and taking the lead in three major capital building projects that have transformed the department. From 2008 to 2011 he was Associate Head of Oxford's Division of Medical Sciences, and from 2011 to 2017 the University's Pro-Vice-Chancellor (Planning and Resources).