This paper reviews the use of behavioural ideas to improve public policy. There needs to be a behavioural take on decision-making itself so that policies are designed in more effective ways. it recounts the beginnings of behavioural sciences as currently conceived and then setting out the massive expansion of interest that has come about since that time. It reports on how such ideas have had a large impact on governments at all levels across the world, but also noting how decision-making itself has been influenced by more policy-relevant ideas. The paper discusses the paradox that the very decision-makers themselves are subject to the same biases as the objects of behavioural economics, which might imply limitations in the choices of such interventions. Here the text of the chapter reengages with the classics of decision-making theory. The chapter notes how behavioural sciences need not depend on a top down approach but can incorporate citizen voice. The paper reviews how citizens and other groups can use behavioural cues to alter the behaviour of policy-makers in socially beneficial ways. The paper discusses how behaviourally informed measures could be integrated within the policy making process in ways that advance the effective use of evidence and nudge decision to make better policies.