Downing Street is the street in London in which the Prime Minister and the Chancellor of the Exchequer live. You can also use Downing Street to refer to the Prime Minister and his or her officials. The Prime Minister arrived back at Downing Street from Paris this morning Downing Street is taking the French opinion polls very seriously indeed. A thoroughfare of Westminster in London, England, off Whitehall. No. 10 Downing Street is the official residence of the first lord of the Treasury, who is usually but not necessarily the prime minister of Great Britain. Nearly all prime ministers have lived at No. 10 since the time of Robert Walpole in the early 1700s. The British government. the street in central London that contains the official houses of the British Prime Minister, at number 10, and the Chancellor of the Exchequer (=chief financial minister) at number