In a cul-de-sac situated off Whitehall, it is 200 metres (660 ft) long, and a few minutes' walk from the Houses of Parliament.

Opposite, for part of the street, the Cabinet Office, initially Treasury, was built to face Whitehall.

Little is known about what was on the site before the mansion, but there is evidence of a brewhouse called 'The Axe', owned by the Abbey of Abingdon, and the premises of the goldsmith Everard Everdyes.

[1] Downing was a soldier and diplomat who served under Oliver Cromwell and King Charles II, and who invested in properties and acquired considerable wealth.

[2][3][4] In 1654, he purchased the lease on land east of St James's Park, adjacent to the House at the Back, and within walking distance of Parliament.

[6] When the Hampden lease expired, Downing received permission to build further west to take advantage of recent developments.

The new warrant issued in 1682 reads: "Sir George Downing ... [is authorised] to build new and more houses further westward on the grounds granted him by the patent of 1663/4 Feb. 23.

"[5] Between 1682 and 1684, Downing built the cul-de-sac of two-storey townhouses with coach-houses, stables and views of St James's Park.

On some occasions Number 11 has been occupied not by the Chancellor of the Exchequer but by the individual considered to be the nominal deputy Prime Minister (whether or not they actually took the title); this was particularly common in coalition governments.

After the 1997 general election, in which Labour took power, a swap was carried out by the new incumbents of the two titles; Tony Blair being a married man with three children living at home, while his counterpart Gordon Brown was unmarried at the time of taking up his post.

[18] In 1974, the Metropolitan Police proposed erecting a semi-permanent barrier between the pavement and carriageway on the Foreign Office side to keep pedestrians off the main part of the street.

The Prime Minister, Harold Wilson, rejected the proposal, feeling that it would appear to be an unacceptable restriction of the freedom of the public.

The trigger was an altercation between Conservative Chief Whip Andrew Mitchell, and the police officers on duty at these gates.

Public access was curtailed by relying on common law powers to prevent breach of the peace[20][23][24] (although its legality has been questioned by a correspondent for New Statesman magazine).

[25] In 2005, Westminster City Council used anti-terrorism powers contained in the Civil Contingencies Act 2004 to formalise the restrictions by means of a traffic management order.

[25] This by implication results in Downing Street being inaccessible to the general public as admittance is only granted by the Police to scheduled visitors, Parliamentary pass holders and members of the accredited press.