How many U.S. ambassadors to the Court of St. James later became presidents of the United States?

The United States Ambassador to the United Kingdom (known formally in the United Kingdom as Ambassador of the United States to the Court of St James) is the official representative of the President and the Government of the United States of America to the Queen and Government of the United Kingdom of Great Britain and Northern Ireland.

Here, the job of ambassador is regarded as the most prestigious position in the United States Foreign Service. There is a very special relationship between the countries. Accordingly, the ambassadorship has been held by various notable politicians, including five who would later become presidents: John Adams, James Monroe, John Quincy Adams, Martin Van Buren and James Buchanan.

Nowadays, the common tendency of American presidents (of both parties) is to appoint keen political fundraisers from previous presidential campaigns, despite the importance and prestige of the office.

The ambassador and the embassy staff at large conduct business at the American Embassy in Grosvenor Square, London. However, Winfield House in Regent's Park is the official residence of the ambassador.