10 Downing Street in the context of "First Lord of the Treasury"

The prime minister of the United Kingdom is the head of government of the United Kingdom. The prime minister advises the sovereign on the exercise of much of the royal prerogative, chairs the Cabinet, and selects its ministers. Modern prime ministers hold office by virtue of their ability to command the confidence of the House of Commons, so they are invariably members of Parliament.

The office of prime minister is not established by any statute or constitutional document, but exists only by long-established convention, whereby the monarch appoints as prime minister the person most likely to command the confidence of the House of Commons. In practice, this is the leader of the political party that holds the largest number of seats in the Commons. The prime minister is ex officio also First Lord of the Treasury (an office often associated with the premiership between 1721 and 1895, after 1902 always united to it, and, after 1905, an official title of the position), Minister for the Civil Service, the minister responsible for national security, and Minister for the Union. The prime minister's official residence and office is 10 Downing Street in London.

A cabinet in governing is a group of people with the constitutional or legal task to rule a country or state, or advise a head of state, usually from the executive branch. Their members are known as ministers and secretaries and they are often appointed by either heads of state or government. Cabinets are typically the body responsible for the day-to-day management of the government and response to sudden events, whereas the legislative and judicial branches work in a measured pace, in sessions according to lengthy procedures.

The function of a cabinet varies: in some countries, it is a collegiate decision-making body with collective responsibility, while in others it may function either as a purely advisory body or an assisting institution to a decision-making head of state or head of government.

The City of Westminster is a London borough with city status in Greater London, England. It is the site of the United Kingdom's Houses of Parliament and much of the British government. It contains a large part of central London, including most of the West End, such as the major shopping areas around Oxford Street, Regent Street, Piccadilly and Bond Street, and the entertainment district of Soho. Many London landmarks are within the borough, including Buckingham Palace, Westminster Abbey, Whitehall, Westminster Cathedral, 10 Downing Street, and Trafalgar Square.

The borough also has a number of major parks and open spaces, including Hyde Park, and most of Regent's Park. Away from central London the borough also includes various inner suburbs, including St John's Wood, Maida Vale, Bayswater, Belgravia and Pimlico. The borough had a population of 204,300 at the 2021 census.

In architecture, a transom is a transverse horizontal structural beam or bar, or a crosspiece separating a door from a window above it. This contrasts with a mullion, a vertical structural member. Transom or transom window is also the customary U.S. word used for a transom light, the window over this crosspiece. In Britain, the transom light is usually referred to as a fanlight, often with a semi-circular shape, especially when the window is segmented like the slats of a folding hand fan. A prominent example of this is at the main entrance of 10 Downing Street, the official residence of the prime minister of the United Kingdom.