President Donald Trump, First Lady Melania Trump and Queen Elizabeth II attend D-Day Commemorations in June 2019 in Portsmouth, England. Getty Images
Princess Elizabeth and Prince Philip look on as President Harry Truman gives a speech in Washington, DC, in November 1951. Getty Images
President Dwight Eisenhower, centre, with Prince Philip, Princess Anne, Queen Elizabeth II, Prince Charles and Captain John Eisenhower at Balmoral Castle, Scotland, in September 1959. Getty Images
Prince Philip, Jacqueline Kennedy, Queen Elizabeth II and President John F Kennedy in the drawing room at London's Buckingham Palace in June, 1961. Getty Images
Queen Elizabeth II with President Richard Nixon at Buckingham Palace in February 1969. Getty Images
President Richard Nixon and British Prime Minister Edward Heath meet Queen Elizabeth II for lunch at Chequers in October 1970. Getty Images
Queen Elizabeth II makes a speech, next to President Gerald Ford, at the White House in Washington, DC, in July 1976. AFP
President Jimmy Carter with Queen Elizabeth II and Prince Philip at Buckingham Palace in May 1977. Getty Images
Queen Elizabeth II and President Ronald Reagan commemorate the 40th anniversary of D-Day in Normandy, France, in June 1984. Getty Images
President Ronald Reagan and Queen Elizabeth II at a gala dinner at Windsor Castle in June 1982. Getty Images
Prince Philip, Queen Elizabeth II, President George Bush and First Lady Barbara Bush attend a dinner at the British Embassy in May 1991. AFP
First Lady Hillary Rodham Clinton, President Bill Clinton and Chelsea Clinton meet Queen Elizabeth II at Buckingham Palace in December 2000. AFP
President George W Bush, Queen Elizabeth II, First Lady Laura Bush and Prince Philip at Buckingham Palace in November 2003. Getty Images
Queen Margrethe of Denmark, Prince Philip, Queen Elizabeth II, French President Jacques Chirac, Bernadette Chirac, President George W Bush, First Lady Laura Bush and Russian President Vladimir Putin attend a commemoration ceremony on the 60th anniversary of D-Day in Arromanches, France, in June 2004. Getty Images
President Barack Obama and First Lady Michelle Obama meet Queen Elizabeth II at Buckingham Palace in April 2009. Getty Images
President Barack Obama and Queen Elizabeth II attend a state banquet at Buckingham Palace in May 2011. Getty Images
President Barack Obama and First Lady Michelle Obama are greeted by Queen Elizabeth II and Prince Philip after landing by helicopter at Windsor Castle in April 2016. Getty Images
President Donald Trump and First Lady Melania Trump with Queen Elizabeth II at Windsor Castle in July 2018. Getty Images
President Donald Trump and Queen Elizabeth II attend a state banquet at Buckingham Palace in June 2019. Getty Images
President Donald Trump, First Lady Melania Trump and Queen Elizabeth II attend D-Day Commemorations in June 2019 in Portsmouth, England. Getty Images
Princess Elizabeth and Prince Philip look on as President Harry Truman gives a speech in Washington, DC, in November 1951. Getty Images
President Dwight Eisenhower, centre, with Prince Philip, Princess Anne, Queen Elizabeth II, Prince Charles and Captain John Eisenhower at Balmoral Castle, Scotland, in September 1959. Getty Images
Prince Philip, Jacqueline Kennedy, Queen Elizabeth II and President John F Kennedy in the drawing room at London's Buckingham Palace in June, 1961. Getty Images
Queen Elizabeth II with President Richard Nixon at Buckingham Palace in February 1969. Getty Images
President Richard Nixon and British Prime Minister Edward Heath meet Queen Elizabeth II for lunch at Chequers in October 1970. Getty Images
Queen Elizabeth II makes a speech, next to President Gerald Ford, at the White House in Washington, DC, in July 1976. AFP
President Jimmy Carter with Queen Elizabeth II and Prince Philip at Buckingham Palace in May 1977. Getty Images
Queen Elizabeth II and President Ronald Reagan commemorate the 40th anniversary of D-Day in Normandy, France, in June 1984. Getty Images
President Ronald Reagan and Queen Elizabeth II at a gala dinner at Windsor Castle in June 1982. Getty Images
Prince Philip, Queen Elizabeth II, President George Bush and First Lady Barbara Bush attend a dinner at the British Embassy in May 1991. AFP
First Lady Hillary Rodham Clinton, President Bill Clinton and Chelsea Clinton meet Queen Elizabeth II at Buckingham Palace in December 2000. AFP
President George W Bush, Queen Elizabeth II, First Lady Laura Bush and Prince Philip at Buckingham Palace in November 2003. Getty Images
Queen Margrethe of Denmark, Prince Philip, Queen Elizabeth II, French President Jacques Chirac, Bernadette Chirac, President George W Bush, First Lady Laura Bush and Russian President Vladimir Putin attend a commemoration ceremony on the 60th anniversary of D-Day in Arromanches, France, in June 2004. Getty Images
President Barack Obama and First Lady Michelle Obama meet Queen Elizabeth II at Buckingham Palace in April 2009. Getty Images
President Barack Obama and Queen Elizabeth II attend a state banquet at Buckingham Palace in May 2011. Getty Images
President Barack Obama and First Lady Michelle Obama are greeted by Queen Elizabeth II and Prince Philip after landing by helicopter at Windsor Castle in April 2016. Getty Images
President Donald Trump and First Lady Melania Trump with Queen Elizabeth II at Windsor Castle in July 2018. Getty Images
President Donald Trump and Queen Elizabeth II attend a state banquet at Buckingham Palace in June 2019. Getty Images
President Donald Trump, First Lady Melania Trump and Queen Elizabeth II attend D-Day Commemorations in June 2019 in Portsmouth, England. Getty Images