Condoleezza Rice, national security adviser and secretary of state in President George W. Bush's administration, joined British Foreign Secretary William Hague at the morning ceremony in Grosvenor Square.
"Statues bring us to face to face with our heroes long after they are gone," Hague said "Ronald Reagan is without question a great American hero; one of America's finest sons, and a giant of 20th-century history. You may be sure that the people of London will take this statue to their hearts."
Hague also brought a message from former Prime Minister Margaret Thatcher, Reagan's staunch ally, whose frail health has made her public appearances very rare.
"She has asked me to say these words to you: Ronald Reagan was a great president and a great man — a true leader for our times," Hague said.
"He held clear principles and acted upon them with purpose. Through his strength and his conviction he brought millions of people to freedom as the Iron Curtain finally came down."
The London statue was commissioned by the Reagan Memorial Fund Trust. It joins images of former presidents Franklin D. Roosevelt and Dwight D. Eisenhower in Grosvenor Square, and will remain there after the U.S. Embassy moves to a new location.