Downing Street is a gated street in Westminster in London that houses the official residences and offices of the prime minister of the United Kingdom and the chancellor of the exchequer 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. Downing Street was built in the 1680s by Sir George Downing.
For more than three hundred years, it has held the official residences of both the First Lord of the Treasury, the office now synonymous with that of the Prime Minister, and the Second Lord of the Treasury, the office held by the Chancellor of the Exchequer. The Prime Minister's official residence is 10 Downing Street, and the Chancellor's official residence is Number 11. The government's Chief Whip has an official residence at Number 12. Over time, government offices and officials came to occupy most of the street's townhouses. The houses on the south side of the street were demolished in the 19th century to make way for government offices now occupied by the Foreign, Commonwealth and Development Office. Opposite, for part of the street, the Cabinet Office, initially Treasury, was built to face Whitehall.