The design required a staged construction and collaboration of the engineers and construction managers. The roof slabs were installed first for support, extending back all the way to the level 4 stairs. Then allowing for a 25m drop (subsequently measured by geomatics) in the horizontal beams as the concrete slabs for each floor were added.
The diagonal support can be seen behind the glass on the east and west sides.
Read next about constructing the Cantilever.