Venezuelan opposition leader Juan Guaido was in London on Tuesday as part of a surprise international trip to revive support for forcing the resignation of the country’s authoritarian leader, Nicolas Maduro. One year ago, Guaido was recognized by the U.S. and over 50 countries as Venezuela’s interim president after Maduro blocked opponents in the last presidential election. However, VOA’s Brian Padden reports that tough U.S. sanctions and diplomatic pressure imposed a year ago have not succeeded to break the socialist president's hold on power.