Comprising a site of 3 hectares (7.4 acres), the building is located on Whitehall within the City of Westminster, central London.

Adjacent to Richmond Terrace is the Curtis Green Building, the headquarters of the Metropolitan Police Service since November 2016 and otherwise known as New Scotland Yard.

[2] The building is located on the site of the Palace of Whitehall, which was the main residence of the English monarchs in London from 1530 until 1698 when most of its structures were destroyed by a fire.

[3] In 1909, a decision was taken to construct a new significant government building on the Whitehall Gardens site, primarily to be used by the Board of Trade.

Opposition to this idea however led to the southern building-line extending no further than that of the neighbouring Whitehall Court and National Liberal Club buildings to the north.

[5] Due to the wishes of Queen Mary and after providing assurances to Parliament, arrangements were made for the preservation of a 16th-century Tudor brick-vaulted wine cellar which had originally been located in Cadogan House, the York Place home of Cardinal Wolsey.

[8] It was then moved 43 feet 6 inches (13.26 m) to one side onto a specially designed steel frame so that a 20-foot (6.1 m) hole could be created on its original site.

[11] In the early 1990s, the MOD recognised that the condition of Main Building was no longer fit for modern business requirements.

At the same time, the MOD was seeking to reduce the number of staff it had within London so that it could make savings by consolidating its built estate.

[12] The contract winner, Modus, was a consortium consisting of Innisfree PFI Funds (40.1% shareholding), Laing Investments (40.1%) and Amey Ventures (19.9%).

New communal spaces were created including a library, restaurant, coffee shop, business & press suite and nursery.

Original historic features of the building were protected and restored during the redevelopment, such as the replacement of oak doors and terrazzo marble floor of the Pillared Hall.

[3] The building was handed back to the MOD in July 2004 and re-occupation by 3,150 staff was completed in September 2004, two months ahead of schedule.

In response, the MOD said that chairs were purchased at a large discount (approximately a third of the normal price); many of the aspects of the refurbishment relating to historic features were required by English Heritage, reflecting the building's grade I listed status; and that staff facilities were generally not subsidised, were required to ensure an acceptable level of staff welfare and to provide a suitable working environment.

[3][20] In April 2002, whilst redevelopment was still under way, the National Audit Office (NAO) considered the extent to which the PFI contract was likely to deliver value for money and the effectiveness of MOD's management of the project.

[3][22][23] The northern tetrastyle portico entrance to the building, on Horse Guards Avenue, is flanked by two large statues, Earth and Water, by the sculptor Sir Charles Wheeler.

Similar figures representing "air" and "fire" were intended to be installed at the south end of the building; however, these were never constructed.

[9][24] The badge of the RAF is carved into stone columns either side of the southern entrance to the building, reflecting its initial use by the Air Ministry.

[11] Beneath Main Building is a three-storey bunker complex housing the Defence Crisis Management Centre (DCMC), otherwise known as "Pindar" after the ancient Greek poet.

[31] In August 2016, The Times newspaper reported that the specialist armed unit of the Ministry of Defence Police which guards Main Building could cease to carry out such duties.