The entrance to the east wing of the building is reached via a paved terrace which forms the roof of the staff restaurant, located at semi-basement level. The roof structure consists of a series of cast in-situ concrete vaults, six metre square in plan, each with a cuboid glazed lantern at the apex. A colonnade of solid brick piers borders the south wall of the restaurant, which runs at an angle to the vaults. The wall is glazed with sliding doors to give views out over a garden. The ceiling space between the vaults and the colonnade is used for services concealed with a suspended ceiling system.
The concrete vaults were cast on plywood moulds and are covered with an upside-down insulated roof system and stone pavers; the soffits are painted and lit with cold cathode tubes set at the springing of the vaults.
The five lanterns project above the terrace, and are lit at night. Each lantern sits on a concrete upstand sealed with a preformed, polyester powder-coated aluminium cloak. The four walls are frameless double-glazed glass units which are bolted together at the corners with the toughened- glass outer panes extended to form a butt joint which is then sealed with silicone; a cable to the light fitting is carried within it. The four glazed units support the polyester powder-coated aluminium lantern lid; it is fitted with a perforated suspended ceiling and with a low-energy downlight.
A polished aluminium light reflector is suspended below each lantern to reflect light onto the vault.
The colonnade is made of precast concrete units supported on stainless- steel angles and solid brick columns at 3m centres.