In 2011, Castledine was terminated as the chief executive of the Institute of Ageing and Health for allegedly having an improper sexual relationship with an 85-year-old patient. He was suspended by the
Nursing and Midwifery Council for 18 months, pending the outcome of an investigation into the alleged misconduct. In January 2014, after a lengthy hearing, the NMC Conduct and Competence Committee found that 11 of the 13 charges of misconduct laid against Castledine were proven and imposed a striking off order. As a result, his knighthood was annulled. He died on 12 October 2018 at the age of 72. ==References==