As an Associate at Renzo Piano Building Workshop in Paris, William completed a variety of internationally recognised projects including:
- Fondation Beyeler, Basel
- Potsdamer Platz, Berlin
- Centre Pompidou renovation, Paris
- Central St Giles, London
- The Modern Wing of the Art Institute of Chicago
- SanPaolo Intesa HQ, Turin
From 2001 until its completion in 2013 William led the design team of the Shard in London.