Adrian Hayday trained as a biochemist, undertook PhD studies in tumour virology and then pursued postdoctoral training at the Massachusetts Institute of Technology (MIT). At MIT he characterised chromosome translocation breakpoints in human B cell lymphomas and contributed to identification of the hitherto unanticipated gamma delta T cell compartment by being the first to describe T cell receptor gamma chain genes.
In 13 years on the faculty at Yale, he helped show that gamma delta T cells illustrate a distinct, unrecognised aspect of lymphocyte biology, including the cells' disproportionate association with tissues rather than with lymphoid organs and their rapid responses to tissue stress.
At a time when tumour immune surveillance was not widely accepted, his lab showed that mice lacking gamma delta T cells are profoundly more susceptible to carcinogens.
His group returned to London in 1998 to establish the Peter Gorer Department of Immunobiology at King's College London. He joined the Cancer Research UK London Research Institute (now part of the Francis Crick Institute) as a joint appointee in 2009.
In recent years, his group has developed a strong programme in human immunology, including clinical trials applying gamma delta T cells in immunotherapy. Among many honours, in 1997 he became the first biologist to win Yale College's most prestigious prize for scholarship, the William Clyde DeVane Medal.