 At the Royal Marsden, Kay helped to design and was the first administrator of an isolation ward for patients with weakened immune systems that was built in 1963.The concept was so successful that a larger version of the ward was opened in 1973 and was equipped for intensive treatment of acute leukaemias.At the time of his retirement as a professor of haematology in 1984, leukaemia had become a largely curable disease.