- Construction commenced in 1861 & was completed in 1868.
- The building was designed by architect George Gilbert Scott who also designed the renaissance hotel at St Pancras station.
- The architecture is in the Italianate style. Scott originally envisaged a gothic design by the then prime minister; Lord Palmerston overruled this and insisted on a more classical style of architecture.
- The building was granted grade 1 listed status in 1970, to prevent it from being demolished by developers
- It was originally 4 separate buildings each for a different department; the foreign office, the India office, the colonial office and the home office.
J E Putney and sons were awarded the contract to carry out the making goods to all walls and ceilings to over 600 rooms & 5 miles of corridors throughout the building, using traditional lime plaster. 5 ceilings were replaced entirely using oak sawn laths and 3 coat haired lime plaster. In addition to this, the fibrous cornice & skirting repairs were also carried out by JE Putney and sons.