David Williams is a career civil servant who served as Permanent Under-Secretary at the Ministry of Defence from April 2021 to November 2025. During his tenure he worked under four Prime Ministers and three Defence Secretaries, overseeing major defence reform programmes and supporting the UK's response to significant international events, including the withdrawal from Afghanistan, the war in Ukraine and conflict in the Middle East. Prior to this, David held senior leadership roles in health, including at the Department of Health and Social Care during the Covid-19 pandemic and East Sussex Hospitals NHS Trust. He was appointed Companion of the Order of the Bath (CB) in the 2020 New Year Honours.