There is abundant evidence of the national policies that are needed to give all children the best possible start in life. Previously in the UK, concerted efforts have been made to implement such policy recommendations in the social, economic, education and welfare sectors. These efforts have led to a sustained reduction in child poverty and improvements in children’s services, which in turn have contributed to improved health and life chances. Currently, however, we are seeing a halting or reversal of the favourable policy direction, resulting in a rise in child poverty and a worsening of the conditions in which families with young children live. From a public health perspective, the unprecedented rise in infant mortality in the most disadvantaged areas of the country is a most disturbing development. These policy and health reversals have been termed “the Great Leap Backwards” and are the focus of this 2019 Sidney Ball Lecture, together with a questioning of what can and should be done about it.