Portsdown Main in better times as seen from James Callaghan Drive looking west. The entrance was centre left between the two guardhouses. The bus shelters were for the employees, and traffic to the site was so heavy that it had its own set of traffic lights.

 The building consisted of three full floors, two levels of penthouses just visible top centre and a basement occupying a quarter of the building area at the western end.

The external 'art deco' style continued inside. This was the main south entrance lobby.

The central main staircase. The banisters were made of metal and used to be polished bright. A film crew used this location in the making of an Agatha Christie film. 

 The layout of the floors was very uniform throughout the building with one corridor looking much like another as is typical of MoD architecture. The floors were laid with genuine Parquet tiles which began lifting after the heating was turned off.