After completing a BSc Hons., with the award of a University Medal, at the University of New England in 1962, Alan was a graduate student at the University of California at Berkeley from 1963 to 1966, completing his PhD in operator theory, under the supervision of Frantisek Wolf.
During his studies at Berkeley he was greatly influenced by Tosio Kato and that association played a prominent part in his subsequent research career. After a postdoctoral year at The Institute for Advanced Study at Princeton he returned to Australia in 1967 to take up a position in the School of Mathematics and Physics at the newly established Macquarie University.
In 1999 he moved to the Australian National University as a Professor in the Centre for Mathematics and its Applications in the School of Mathematical Sciences, (now called the Mathematical Sciences Institute), from which he retired in 2014.
Alan is particularly famous for his role in the resolutions of the Calderon conjecture on singular integrals and the Kato square root problem both of which have had a massive impact in harmonic analysis and partial differential equations. He will also be well remembered though for his abundant and natural friendliness with students and colleagues of all levels and the care and inspiration given to his graduate students and postdocs. His research achievements have also been recognised through election to the Australian Academy of Science in 1986, the award of Moyal Medal by Macquarie University in 2002 and the Hannan Medal by the Australian
Academy of Science in 2015.
Professor McIntosh is survived by his wife Evelina and children Debbie, Adrian, Keith and Jennifer.
Professor Neil Trudinger.