The 1917 Treasury building has been transformed from a labyrinth of neglected spaces into an efficient working environment. The Feilden+Mawson Conservation Management Plan and detail design allowed for the creation of open-plan offices, the opening up of lightwells for amenity and ventilation, the addition of an extra floor at roof level around the central courtyard and the restoration of elevations and historic fabric.

Feilden+Mawson were part of the design team as technical specialists and Conservation Architects, led by Foster and Partners, on the two phases of redevelopment from 1998 to 2004 and continue to work on the building.