Peter Mathias formed the Holder and Mathias Partnership with Tim Holder in 1968.  The practice is now an RIBA Chartered Practice, has achieved Investor in People status, has been acknowledged as one of the Top 50 Employers in the UK Construction Industry (Building Magazine October 2007) and has consistently been in the AJ Top 100 list of UK architectural practices.

As an active member of the Royal Society of Architects in Wales, Peter served on its Council from 1975 to 1989 and as President from 1985 to 1987. He also served as an RIBA Council Member from 1981 to 1987, chairing the Sound Practice Steering Group from 1985 to 1987. More recently he was invited to chair an informal Think Tank of principals of practices in the region.

Peter has combined his love of music with a strong sense of public service, firstly as a Director of The Welsh National Opera from 1990 to 1995 and then as a Governor of The Welsh College of Music and Drama from 1996 to 2007 where he laid the foundation of the present performing arts centre project. Peter's enthusiasm for performing arts has encouraged Holder Mathias to become both Guild Members and commercial sponsors of The Wales Millennium Centre, which the practice continues to support.