Boris Johnson has hit out at US presidential candidate Mitt Romney for comments suggesting Britain is not ready to stage the Olympic Games.
Johnson fired up a large crowd in Hyde Park, saying: "There's a guy called Mitt Romney who wants to know whether we're ready. Are we ready?"
Earlier, Romney backtracked after meeting UK PM David Cameron and predicted a "very successful" Olympics.
Romney's remarks came on the first official day of a week-long tour that is to include stops in Israel and Poland.