Dr Butler has a substantive position as a consultant physician at Addenbrooke's Hospital in Cambridge and since April 2024 was appointed End of Life Care Clinical Lead at CUH. Between March 2020 to October 2024, he took a particular research interest in respiratory infections such as COVID-19 (caused by the SARS-COV-2 virus) in hospitals and as such became the Principal Investigator for the now concluded Addenbrooke's Air Disinfection Study (AAirDS) which is the topic for his talk. Prior to this he took an interest in indoor air quality in schools and sits on the Scientific Advisory Group to the CLASS-ACT study, the world's largest randomised controlled trial examining the effect air cleaning has in English primary schools. Prior to AAirDS, he worked closely with headteachers from across the country helping them to mitigate the effects of the COVID-19 pandemic and featured on podcasts via the NAHT as well as on BBC Breakfast.