WILLIAM LONG is global co-chair of Sidley’s highly ranked Privacy and Cybersecurity practice and heads the EU Data Protection group. He is also a member of the firm’s top-ranked Crisis Management and Strategic Response team. He also serves on the firm’s AI Working Group. William advises international clients on a wide variety of AI, GDPR, cyber incident, data protection, privacy, information security, social media, e-commerce, and other regulatory matters.
William has been a member of the European Advisory Board of the International Association of Privacy Professionals (IAPP) and on the DataGuidance panel of data protection lawyers. He is also on the editorial board of e-Health Law & Policy and also assists with dplegal (“data privacy” legal), a networking group of in-house lawyers in life sciences companies examining international data protection issues.
William was previously in-house counsel to one of the world’s largest international financial services groups. He has been a member of a number of working groups in London and Europe looking at the EU regulation of e-commerce and data protection and spent a year at the UK’s Financial Law Panel (established by the Bank of England) as assistant to the chief executive working on regulatory issues with online financial services.
William has received acknowledgement from numerous industry ranking guides:
- Chambers UK 2024 – Ranked for Data Protection and Information Law, with sources telling the publication “he does a phenomenal job in taking a complex subject and simplifying it for us,” and “his extensive network and expertise makes him able to provide thorough yet pragmatic advice.”
- The Legal 500 UK 2024 – Recognized for Data protection, Privacy and Cybersecurity, where sources say “Client -focused. Accommodating. Well-connected within industry groups – particularly William Long.”.
- Chambers UK 2023 – Ranked for Data Protection and Information Law, with clients saying “William is extremely knowledgeable on GDPR/EU privacy laws and how they apply to cross-border businesses. He is also attentive to developments that may affect us and reaches out proactively to inform us.”
- The Legal 500 UK 2023 – Recognized for Data Protection, Privacy and Cybersecurity, where one client comments “I particularly appreciate William’s no-fuss demeanor, and quiet, efficient execution of every task. Without any fanfare, the work is undertaken, timely delivered, and always reflective of an application of the law within the context of commercial realities.”
- Who’s Who Legal 2023 – Ranked as a Thought Leader for Data Privacy and Protection and Data Security and as a Global Leader for Data Privacy and Data Protection, Data Security and Data Information Technology.
- BTI Client Service All-Stars 2022 – Named in this annual report for providing incomparable level of client service excellence.
- Chambers UK 2022 – Ranked for Data Protection and Information Law, with sources telling the publication “he combines his great expertise with a very friendly approach in dealing with clients.”
- The Legal 500 UK 2022 – Recognized for Data Protection, Privacy and Cybersecurity, where one client comments that he “is an international top expert in the field of privacy and data protection: he combines his great expertise with a very friendly approach in dealing with clients, which is very important for a positive relationship.”
William is also the author of a new book on the EU General Data Protection Regulation and a contributor to a number of books on data protection, including leading legal textbooks published by BNA in the area of privacy, cloud computing and the use of health data. William has been interviewed widely for his thought leadership, including in such leading publications as the international New York Times, Financial Times and The Guardian and writes for a number of publications, including Thomson Reuters, Law360, and Global Data Review.