Charlie travels to America to meet Leo Villareal, the artist behind the project. He gets together with the Chewing Gum Man on Millennium Bridge and explores the varied history of London Bridge.
As the work to light the bridges begins, an Egyptian goose lays an egg, putting the tight schedule in a spin. And Charlie goes dangling off the side of London Bridge.
After years of planning, the big day arrives as 69,000 lights illuminate four of London's most iconic bridges in the world's longest piece of public art