What is the official address and residence of the Prime Minister of the United Kingdom?

Downing Street in London is more than just an address; it's the heart of British government. The street itself is named after Sir George Downing, who had houses built there in the 1680s. Number 10 became the Prime Minister's official residence somewhat accidentally. King George II offered it to Sir Robert Walpole in 1732, but Walpole accepted it only as a gift to his office, not for himself. Since then, it has served as both the Prime Minister's residence and their office. It's where they meet with their cabinet, host world leaders, and make some of the most important decisions affecting the country. While Buckingham Palace is the official residence of the monarch, and other addresses might be associated with government functions, Number 10 Downing Street is specifically and uniquely tied to the office of the Prime Minister, making it the correct answer. It's a relatively modest building, which is part of its charm and a symbol of its accessibility.