12 Downing Street

12 Downing Street is one of the buildings situated on Downing Street in the City of Westminster in London, England. It has been traditionally used as the office of the Chief Whip although the upper floor forms part of the residential apartment for the Prime Minister of the United Kingdom. It has been owned and used by the Crown since 1803, first housing the Judge Advocate General of the Armed Forces and then the Colonial Office, before the office of the Chief Whip moved into the premises in 1879 until 2001. It is a Grade II listed building.

The offices of the Prime Minister in 10 Downing Street have spread into 12 Downing Street, connected by a corridor which runs through 11 Downing Street. Under the current government, the building is being used to house the Prime Minister's Press Office and Strategic Communications Unit. Although historically the house was used as the office of the Chief Whip, they are now located in 9 Downing Street. The upper floor of 12 Downing Street forms part of the Prime Minister's personal apartment. This stretches from number 12 across to number 10 as a joint apartment.

The land which 12 Downing Street is built on was first sold by Charles Downing to James Steadman in 1723. The house was then sold in 1772 to William Maseres, who leased it three years later to Henry Hunt. This lease was bought out by Simon Frazer, who also acquired Maseres' stake in the property. After Frazer's death in 1783, it was sold by the executors to James Martin, who in turn sold it to the East India Company in 1803. It was purchased by the Crown in 1803, and was first used to house the Judge Advocate General of the Armed Forces. In 1827, it was taken over by the Colonial Office.

...
Wikipedia