William attended Talgarth School and Gwernyfed High School. He gained a scholarship to read Modern Languages (French and German) at Pembroke College, Oxford and graduated in 1986. A qualified teacher, he has taught French and German at a number of schools in Wales and the Marches and was latterly Head of German at Hereford Sixth Form College, where he was also the European Officer.
William has served as County Councillor for Talgarth since 2004 and has been active in rural regeneration projects, including the restoration of Talgarth Mill, one of six projects across the UK to win financial support from the BIG Lottery in association with the BBC's Village SOS programme. He is a former Member and Audit Scrutiny Chair of the Brecon Beacons National Park Authority. Whilst on that body he was active in the campaign for direct elections to the National Park Authorities in Wales.
William was also a founding board member of Wales in Europe and currently serves as Chair of the Wales Council European Movement. In addition, William is a Council Member of the European Liberal Democrats (ELDR) and works closely with Liberal sister-parties across the continent. He is a member of the FUW and was until recently Vice Chair of Tourism Partnership Mid Wales, which is based in Machynlleth. He is a Governor of Talgarth CP School and Gwernyfed High School. William is a member of the Lloyd George Society, where he also serves on the committee.
William was the National Assembly Regional Assembly Member for Mid & West Wales from 2011 to 2016. He lives with his family on their organic farm in the Black Mountains, near Talgarth, Powys.