The American ambassador's residence in London is called Winfield House. It is located in Regent's Park, central London, and has been the official residence of the United States Ambassador to the United Kingdom since 1955. The property includes 12 acres of grounds, making it the second largest private garden in London after Buckingham Palace. The mansion is a 35-room, neo-Georgian style house originally built for American heiress Barbara Woolworth Hutton. It is known for hosting diplomatic and social events and is not typically open to the public due to its exclusivity and privacy in Regent’s Park.