Firstly, since the new building occupies a transitional position it needed to be lower than the New Street Square building. Secondly, the scale change between the West and East elevation required a governing architectural rationale, which after much study emerged as a cascade of double storey stepped terraces rotating around the southern vertical hinge.
The hinge itself was then expressed as a translucent glazed staircase, filtering natural light during the day and glowing as a vertical white beacon at night.
The external envelope for the building is composed almost entirely of glass. The core cladding is expressed with very pale grey opaque glass vertical panels, whilst the main clear glazing to the offices is expressed as a multi-faceted and reticulated surface. These diamond-like facades generate multiple complex reflections, capturing light and constantly changing in both pattern and appearance throughout the day. This highly modelled façade also acts as a deliberate counterpoint to the strong horizontality of the New Street Square building opposite, and is a subtle reference to the historic diamond dealing district of Hatton Garden. The prime quality of ce space within the building bene ts from high levels of natural light and breath-taking views across London from the higher levels of the building.
The overall form of the building is then tied together as a single cohesive composition by means of the introduction of a Northern vertical service core to mirror the Southern staircase connected together through the entire building. The ground floor of the building is set back to emphasise the volumes of the superstructure of ce space above it. The main entrance lobby that runs most of the length of the New Fetter Lane elevation is expressed as a single clear volume viewed through a full height and full width glass wall made up of gigantic glazed panels supported by barely visible glass fins.
Sustainability has also been a key factor throughout the development of the design. The building achieves a BREEAM Excellent rating and offers a substantial reduction in CO2 emissions when compared to current Building Regulations.