Data ethics is a cross-cutting discipline that critically assesses the wider societal impact of technology and data and produces actionable recommendations for other data professionals. It involves thinking about fairness, accountability, the law, moral dilemmas, and risks involved in the creation of technology and data products and policies. Due to the complexity and multidisciplinary demands of this field, there is a need for a designated data ethics position in the public sector that would be responsible for providing research and expertise on data ethics, and acting as a champion and change agent. This paper outlines what the role of the data ethicist would entail, for instance: enabling and empowering others to implement data ethics best practice in their work; demonstrating how to apply ethical principles in practice; communicating effectively to explain and raise awareness of data ethics issues; listening, convening, advising and mediating between various parts of the organisation. It also entails creating a space for others to ask questions, express concerns, and discuss ethical dilemmas. The paper connects the practical experience of data ethics professionals and the emerging theory and research on data ethics with primary data gathered during workshops and a comprehensive survey with data ethics practitioners in all sectors. The research identifies key skills for effective data ethics work and provides a description of a designated Data Ethicist role for the Digital, Data and Technology (DDaT) Professional Capability Framework in the United Kingdom.