Give a stream of consciousness and then the final answer. Winfield House is a mansion set in 12 acres (4.9 ha) of grounds in Regent's Park, the second largest private garden in central London, after that of Buckingham Palace. Since 1955, it has been the official residence of the United States Ambassador to the Court of St. James's. It is Grade II listed as an "exceptional ambassador's residence and as a notable Neo-Georgian town house containing numerous features of note."

Answer this question: where does the us ambassador live in london?
To answer the above question, the relevant sentence is: Since 1955, it has been the official residence of the United States Ambassador to the Court of St. James's.
So, the final answer is Winfield House.