10 Downing Street in London is the official residence and office of the prime minister of the United Kingdom, as the first lord of the treasury. Colloquially known as Number 10, the building is located in Downing Street, off Whitehall in the City of Westminster.

It is over 300 years old, is a Grade I listed building, and contains approximately 100 rooms. A private residence for the prime minister occupies the third floor and there is a kitchen in the basement. The other floors contain offices and conference, reception, sitting and dining rooms where the prime minister works, and where government ministers, national leaders, and foreign dignitaries are met and hosted. At the rear is an interior courtyard and a terrace overlooking a garden. Number 10 is adjacent to St James's Park, approximately from Buckingham Palace, the official residence of the British monarch in London, and is near the Palace of Westminster, the meeting place of both Houses of Parliament.

Originally three houses, Number 10 was offered to Robert Walpole by King George II in 1732. Walpole accepted on the condition that the gift was to the office of First Lord of the Treasury, rather than to himself personally. The post of First Lord of the Treasury has, for much of the 18th and 19th centuries and invariably since 1905, been held by the prime minister. Walpole commissioned William Kent to join the three houses and it is this larger house that is known as Number 10 Downing Street.

Despite its size and convenient location near to Parliament, few early prime ministers lived at 10 Downing Street. Costly to maintain, neglected, and run-down, Number 10 was scheduled to be demolished several times, but the property survived and became linked with many statesmen and events in British history. In 1985 Prime Minister Margaret Thatcher said Number 10 had become "one of the most precious jewels in the national heritage"., in letter from Margaret Thatcher used as a preface to the book.

The Prime Minister's Office, for which the terms Downing Street and Number 10 are metonyms, lies within the 10 Downing Street building and is part of the Cabinet Office. It is staffed by civil servants and special advisers.

10 Downing Street is property of His Majesty's Government. Its registered legal title is held in the name of the secretary of state for housing, communities and local government, and the secretary of state is a corporation sole.

History of the building

Original Number 10 Number 10 Downing Street was originally three properties: a mansion overlooking St James's Park called "the House at the Back", a town house behind it, and a cottage. The town house, from which the modern building gets its name, was one of several built by Sir George Downing, 1st Baronet between 1682 and 1684.

Downing, a noted spy for Oliver Cromwell and later King Charles II, invested in property and acquired considerable wealth. In 1654, he purchased the lease on land south of St James's Park, adjacent to the House at the Back within walking distance of parliament. Downing planned to build a row of terraced town houses "for persons of good quality to inhabit in ..." The street on which he built them now bears his name, and the largest became part of Number 10 Downing Street.

Straightforward as the investment seemed, it proved otherwise. The Hampden family had a lease on the land that they refused to relinquish. Downing fought their claim, but failed and had to wait 30 years before he could build. When the Hampden lease expired, Downing received permission to build on land further west to take advantage of more recent property developments. The new warrant issued in 1682 reads: "Sir George Downing ... [is authorised] to build new and more houses ... subject to the proviso that it be not built any nearer than 14 feet of the wall of the said Park at the West end thereof". Between 1682 and 1684, Downing built a cul-de-sac of two-storey town houses with coach-houses, stables and views of St James's Park. Over the years, the addresses changed several times. In 1787, Number 5 became "Number 10".

Downing employed Christopher Wren to design the houses. Although large, they were put up quickly and cheaply on soft soil with shallow foundations. Winston Churchill wrote that Number 10 was "shaky and lightly built by the profiteering contractor whose name they bear".

The upper end of the Downing Street cul-de-sac closed off the access to St James's Park, making the street quiet and private. An advertisement in 1720 described it as "a pretty open Place, especially at the upper end, where are four or five very large and well-built Houses, fit for Persons of Honour and Quality; each House having a pleasant Prospect into St James's Park, with a Tarras Walk". The cul-de-sac had several distinguished residents: George Granville, 1st Baron Lansdowne from 1692 to 1696 and the Earl of Grantham from 1699 to 1703.

Downing did not live in Downing Street. In 1675, he retired to Cambridge, where he died in 1684, a few months after building was completed. In 1800, the wealth he had accumulated was used to found Downing College, Cambridge, as had been his wish should his descendants fail in the male line. Downing's portrait hangs in the entrance hall of Number 10.

History of the "House at the Back" before 1733

The "House at the Back", the largest of the three houses which were combined to make Number 10, was a mansion built in about 1530 next to the Palace of Whitehall. Rebuilt, expanded, and renovated many times since, it was originally one of several buildings that made up the "Cockpit Lodgings", so-called because they were attached to an octagonal structure used for cock-fighting. Early in the 17th century, the Cockpit was converted to a concert hall and theatre; after the Glorious Revolution of 1688, some of the first cabinet meetings were held there secretly.

For many years, the "House at the Back" was the home of Thomas Knyvet, Keeper of Whitehall Palace, famous for capturing Guy Fawkes in 1605 and foiling his plot to assassinate King James I. The previous year, Knyvet had moved into a house next door, approximately where Number 10 is today.

From that time, the "House at the Back" was usually occupied by members of the royal family or the government. Princess Elizabeth, eldest daughter of King James I, lived there from 1604 until 1613 when she married Frederick V, Elector Palatine and moved to Heidelberg. She was the grandmother of King George I, the Elector of Hanover, who became King of Great Britain in 1714, and was a great-grandmother of King George II, who presented the house to Walpole in 1732.

George Monck, 1st Duke of Albemarle, the general responsible for the Restoration of the Monarchy in 1660, lived there from 1660 until his death in 1671. As head of the Great Treasury Commission of 1667–1672, Albemarle transformed accounting methods and allowed the Crown greater control over expenses. His secretary, George Downing, who built Downing Street, is thought to have created these changes. Albemarle is the first treasury minister to have lived in what became the home of the First Lord of the Treasury and prime minister.

In 1671, George Villiers, 2nd Duke of Buckingham took possession when he joined the Cabal Ministry. At considerable expense, Buckingham rebuilt the house. The result was a spacious mansion, lying parallel to Whitehall Palace with a view of St James Park from its garden.

After Buckingham retired in 1676, Lady Charlotte Fitzroy, Charles II's daughter, moved in when she married Edward Lee, 1st Earl of Lichfield. The Crown authorised extensive rebuilding which included adding a storey, thus giving it three main floors, an attic and basement. This structure can be seen today as the rear section of Number 10. (See Plan of the Premises Granted to the Earl and Countess of Lichfield in 1677)British History Online, From: 'No. 10, Downing Street ', Survey of London: volume 14: St Margaret, Westminster, part III: Whitehall II (1931), pp. 113–141. Date accessed: 22 July 2008. The likely reason that repair was required is that the house had settled in the swampy ground near the Thames, causing structural damage.The diarist Pepys recorded a high tide when Whitehall was under water and it is known that buildings in the area require deep foundations to avoid settling. Like Downing Street, it rested on a shallow foundation, a design error that caused problems until 1960 when the modern Number 10 was rebuilt on deep pilings.

The Lichfields followed James II into exile after the Glorious Revolution. Two years later in 1690, William III and Mary II gave the "House at the Back" to Hendrik van Nassau-Ouwerkerk, a Dutch general who had assisted in securing the Crown for the Prince of Orange. Nassau, who Anglicised his name to "Overkirk", lived there until his death in 1708.

The "House at the Back" reverted to the Crown when Lady Overkirk died in 1720. The Treasury issued an order "for repairing and fitting it up in the best and most substantial manner" at a cost of £2,522. The work included: "The Back passage into Downing street to be repaired and a new door; a New Necessary House to be made; To take down the Useless passage formerly made for the Maids of Honour to go into Downing Street, when the Queen lived at the Cockpit; To New Cast a great Lead Cistern & pipes and to lay the Water into the house & a new frame for ye Cistern".

The name of the "House at the Back" changed with the occupant, from Lichfield House to Overkirk House in 1690 to Bothmer House in 1720.

First politician and "head of government" in the house Johann Caspar von Bothmer, Premier Minister of the Electorate of Hanover, head of the German Chancery and adviser to George I and II, took up residency in 1720. Although Bothmer complained about "the ruinous Condition of the Premises", he lived there until his death in 1732. Even though Count von Bothmer was not British, he was a subject of George I and George II and the first politician and head of a government who resided in 10 Downing Street.

First Lord's house: 1733–1735

When Count Bothmer died, ownership of the "House at the Back" reverted to the Crown. George II took this opportunity to offer it to Robert Walpole, often called the first prime minister, as a gift for his services to the nation: stabilising its finances, keeping it at peace and securing the Hanoverian succession.

Walpole did not accept the gift for himself.See letter, dated, "Downing Street, 30 June 1742", from Horace Walpole to Horace Mann: "I am writing to you in one of the charming rooms towards the Park: it is I am willing to enjoy this sweet corner while I may, for we are soon to quit it. Mrs. Sandys came yesterday to give us warning; Lord Wilmington has lent it to them. Sir Robert might have had it for his own at first: but would only take it as First Lord of the Treasury. He goes into a small house of his own in Arlington Street, opposite to where we formerly lived". (Horace Walpole's Letters, ed. Cunningham, 1857, I, p. 246.) British History Online, From: 'No. 10, Downing Street ', Survey of London: volume 14: St Margaret, Westminster, part III: Whitehall II (1931), pp. 113–141. Date accessed: 21 July 2008. He proposedand the King agreedthat the Crown give the properties to the Office of First Lord of the Treasury. Walpole would live there as the incumbent First Lord, but would vacate it for the next one.