Embodying ideals of sustainability, prefabrication and flexibility, Tooley Street – part new build, part refurbishment – represents a significant step forward in speculative office design. Wedged between narrow urban side-streets, a raised railway viaduct and existing Victorian buildings, a new exposed concrete form evolves through the innovative prefabrication of structure, wall and soffit. The engineering is integrated into the fabric of the architecture: nothing can be taken away and nothing need be added. Two barrel vault roofs are placed on top of the concrete frame to augment the internal spatial experience and create an identifiable external form. An internal street accommodating the building’s public areas, vertical circulation and services zones organises the interior, dividing the floorplates into two wings. The lower floors of the refurbished buildings accommodate a restaurant, bar and retail units to provide an active edge to Tooley Street, whilst the upper six floors offer 200,200 square feet of flexible office space.