In 1948, Bowlby hired Robertson, a trained naturalistic observer, to help him observe children whom were separated from their parents by hospitalization and institutionalization. In 1950, Robertson felt compelled to act… so on a very low budget, minimum training, a hand-held camera and his heart he made a deeply moving film: A two-year-old-goes-to-hospital (1953) The target child was randomly selected and the hospital’s clock on the wall was proof for video recording being made at regular periods of the day. This film, together with Spitz's Grief: a peril in infancy helped improve conditions for hospitalized children.
At this time, Bowlby’s work caught the eye of Ronald Hargreaves of World Health Organization (WHO), so he was asked to write a report on the mental health of homeless children in post-war Europe. This report was first published in 1951 as Maternal Care and Mental Health by the WHO, sold nearly 400 000 copies and was translated into 14 languages. A second edition was published in 1965, entitled Child care and the growth of love and with review chapters by Mary Ainsworth.