Alun was born in Caerphilly and studied architecture at the University of Bath, and at the University of Cambridge. In 1994, he wrote an MPhil on reconstruction of Alberti’s Church of San Sebastiano in Mantua, which formed part of a research project on Alberti's work at the Palazzo Te in Mantua led by Robert Travernor and Joseph Rykwert.
After graduating, he worked for Caruso St John Architects as project architect for the New Art Gallery, Walsall, before establishing Dow Jones Architects in 2000 with Biba Dow.
He has led many projects including Maggie’s Cancer Care, the Garden Museum and Leach Pottery in St Ives.
Alun has taught extensively at schools of architecture, including fifteen years teaching diploma units at the AA, London Met and Kingston School of Architecture. He has been a visiting critic and lecturer at numerous universities across the UK and Ireland and has lectured about the work of the practice in Europe and China. He is currently an RIBA external examiner at Nottingham School of Architecture
Alun is a member of the Worshipful Company of Architects and The Art Worker's Guild. He is Civic Trust Award assessor and sits on the South Downs National Parks Design Review Committee.