Tens of thousands of protesters are expected to cram central London's streets, ahead of U.S. President Donald Trump's talks with British Prime Minister Theresa May.
The June 4 talks between Trump and May, to be held at 10 Downing Street, come a day after the U.S. leader was honored with a lavish state banquet hosted by Queen Elizabeth.
"I am so glad that we have another opportunity to demonstrate the immense importance that both our countries attach to our relationship," the queen said in her speech at the banquet.
Trump returned the praise for the "special relationship" between Washington and London, and paid homage to the anniversary of the D-Day invasion of Normandy during World War II, on June 6, 1944.
"We affirm the common values that will unite us long into the future: freedom, sovereignty, self-determination, the rule of law, and reverence for the rights given to us by Almighty God," he said in prepared remarks.
Trump's talks with May come on the second day of his three-day state visit to Britain.
Public opinion polls show the U.S. president is widely unpopular among Britons, and police have planned for large crowds to jam central London during the June 4 event.
A giant inflatable blimp depicting Trump as a pouting baby in a diaper will fly above Parliament Square for two hours.
Police will close the road directly outside Downing Street as a security measure.
Ahead of his arrival in Britain, Trump traded jibes with London's mayor, Sadiq Khan.