U.S. President Donald Trump and first lady Melania Trump arrive at Stansted Airport, Britain, July 12 2018.

British Prime Minister Theresa May and her husband Philip stand together with U.S. President Donald Trump and First Lady Melania Trump at the entrance to Blenheim Palace, where they are attending a dinner with specially invited guests and business leaders, near Oxford, Britain, July 12, 2018. REUTERS/Kevin Lamarque

People inflate a helium filled Donald Trump blimp which they hope to deploy during The President of the United States' upcoming visit, in London, Britain, June 26, 2018.

Demonstrators protest next to the specially erected fence surrounding the U.S. ambassador's residence, Winfield House, where U.S. President Donald Trump and the First Lady Melania Trump are staying, in London, Britain, July 12, 2018.

Demonstrators protest outside the grounds of Blenheim Palace, where U.S. President Donald Trump and the First Lady Melania Trump are attending a dinner with Britain's Prime Minister Theresa May and business leaders, near Oxford, Britain, July 12, 2018.

U.S. President Donald Trump and Melania Trump arrive at Winfield House, residence of the U.S. ambassador to the United Kingdom, in London, England, July 12, 2018.

U.S. President Donald Trump leads British Prime Minister Theresa May by the hand as they climb the steps to the entrance of Blenheim Palace, where they are attending a dinner with other specially invited guests and business leaders, near Oxford, Britain, July 12, 2018. Will Oliver/Pool via REUTERS

Demonstrators protest next to the specially erected fence surrounding the U.S. ambassador's residence, Winfield House, where U.S. President Donald Trump and the First Lady Melania Trump are staying, in London, Britain, July 12, 2018.

British Prime Minister Theresa May and her husband Philip stand together with U.S. President Donald Trump and First Lady Melania Trump at the entrance to Blenheim Palace, where they are attending a dinner with specially invited guests and business leaders, near Oxford, Britain, July 12, 2018.

U.S. President Donald Trump and the first Lady Melania Trump leave the U.S. ambassador's residence, Winfield House, on their way to Blenheim Palace for dinner with Britain's Prime Minister Theresa May and business leaders, in London, Britain, July 12, 2018.

A U.S. military helicopter flies in low over Regent's Park on its way to the U.S. ambassador's residence, Winfield House, as U.S. President Donald Trump and First Lady Melania Trump arrive for their first official visit to Britain, in London, Britain, July 12, 2018.

British Prime Minster Theresa May and her husband Philip stand together with U.S. President Donald Trump and First Lady Melania Trump at the entrance to Blenheim Palace, where they are attending a dinner with specially invited guests and business leaders, near Oxford, Britain, July 12, 2018.

A demonstrator protests next to the specially erected fence surrounding the U.S. ambassador's residence, Winfield House, where U.S. President Donald Trump and the First Lady Melania Trump are staying, in London, Britain, July 12, 2018.

Pro-Trump demonstrators protest outside the grounds of Blenheim Palace, where U.S. President Donald Trump and the First Lady Melania Trump are attending a dinner with Britain's Prime Minister Theresa May and business leaders, near Oxford, Britain, July 12, 2018.