Ford predicted that human blood group polymorphisms might be maintained in the population by providing some protection against disease. Six years after this prediction it was found to be so, and furthermore, heterozygous advantage was decisively established by a study of AB x AB crosses. His magnum opus was "Ecological genetics", which ran to four editions and was widely influential. He laid much of the groundwork for subsequent studies in this field, and was invited as a consultant to help set up similar research groups in several other countries.