He was appointed Foundation Professor of Computer Science at the Australian National University in 1978.
In March 1998 he became the Statutory Professor of Computing Science in the University of Oxford.
In March 2005 he took up a 5-year position as ARC Federation Fellow in the Mathematical Sciences Institute and the Research School of Information Sciences and Engineering at the Australian National University.
He was also Visiting Professor at the University of Oxford Sept 2005 - Sept 2011.
In March 2010 he became a Distinguished Professor of Mathematics and Computer Science with a joint appointment in the Mathematical Sciences Institute and the Research School of Computer Science at the Australian National University. Since September 2011 he has been an Emeritus Professor.
Chief Investigator with J. Cannon and D. Stehlé in the ARC Discovery grant DP0880724 Integral lattices and their theta series.
Chief Investigator with B. B. Zhou in the ARC Discovery grant DP0985271 An integrative and interactive approach for co-estimation of multiple sequence alignment and phylogeny reconstruction.
Chief Investigator with M. Hegland et al in the ARC Linkage Project LP110200410 Robust numerical solution of partial differential equations on petascale computer systems with applications to tsunami modelling and plasma physics.