Cyril Burt was undoubtedly the most important member of this group of psychologists. For over forty years he pioneered the application of psychological theory to education, to the study of children's development, and to the assessment of mental qualities. His appointment to the London County Council in 1913 marked him out as ‘the first official psychologist in the world’; and provided both an inspiration and a role-model for the school psychological services and the child guidance movement. He adapted the Binet-Simon mental and scholastic tests for English schoolchildren and acted as a tireless exponent of their practical and theoretical virtues. His studies of delinquent and backward children rapidly established themselves as classic works of applied psychology.

Burt distinguished himself as an academic as well as a practical psychologist. In 1932 he succeeded Spearman as professor of psychology at University College, London, then the senior position in the discipline in the United Kingdom; he consequently exercised an enormous influence over the training of aspirant educational psychologists. He struggled to provide the discipline with solid theoretical foundations, seeking in factor analysis ‘a few, permanent, and pregnant concepts by means of which we can describe both persons and traits’. His influence continued to be felt outside the scientific community. The Consultative Committee of the Board of Education lent heavily on his evidence in preparing its cycle of reports on psychological tests, on the education of adolescents and of children in primary and infant schools, and on the organisation of secondary education.