This Christmas Special (Part 1) features Professor Mike Kelly, who is Senior Visiting Fellow in the Department of Public Health and Primary Care at the Institute of Public Health and a member of St John's College at the University of Cambridge. Mike is the Ex Director of NICE, where he spent over 10 years leading the organisation to support people working in the public health industry to use evidence-based methodologies.In part one of our discussion we cover Mike's experience working in public health across a huge range of research topics from the prevention of non-communicable disease to end of life care, all of which have close links to behaviour change and other social matters. Through his work at NICE he came across some criticism for being part of a 'nanny state' and trying to do more than simply advise people on how to live healthily. Mike takes us through how science and advice can face stumbling blocks when being recommended to local authorities and even individuals, as well as how the approach to public health has moved from a macro or social scale (environment) to a much more micro scale (individual medications etc), and how this might well be shifting back to a realisation that 'we are the way we live'.Finally, Mike discusses the problems we face translating ideas and languages between sociology, biology and behavioural science, and how we then implement those ideas.Part two will be out Friday 20th December as a Christmas treat, and will unpick Mike's applications of behavioural science, including nudge theory and choice architecture.