Keith Williams Architects will design the redevelopment of Fairfield Halls Concert Hall and Arts Venue in Croydon, South London.
The practice won the design competition, beating John McAslan & Partners and DSDHA.
The long-term redevelopment will involve overhauling the 1962 venue, which was used as a backdrop in the film The Da Vinci Code.
The Fairfield Halls have excellent acoustics and house a 1,700-seat concert hall, the 750-seat Ashcroft Theatre community performance venue, as well as meeting spaces and an art gallery.
Croydon Council launched an official journal of the EU (OJEU) in 2009 to redevelop the halls to cater to a larger proportion or hte population and to improve usage within the building.