Towards the end of his long life Bowlby advised one of his former research students: ‘Always choose a central topic when doing research. That way you know you can get sufficient data. That’s why I studied separation. You can’t miss it. Whatever people say, it is there in the data’ (Hamilton, 1991). As we have seen, Bowlby’s insistence that people had missed the significance of separation and loss as a cause of unhappiness, delinquency and psychiatric illness met a receptive audience in the post-war era of recuperation and reparation. The early work on loss by Bowlby and his associates comprised a systematic description of the psychological reactions to separation and bereavement in children and adults (Bowlby, 1953b; Bowlby et al., 1952c; Parkes, 1964); once Attachment Theory was in place, he could then go on to develop a theoretical account of mourning, based on psychoanalysis but supplemented by the insights of ethology (Bowlby, 1980).