Night Waves

Philip Dodd visits a new exhibition at Tate Modern in London with famous artworks by three pioneering figures from 20th century art. They are Marcel Duchamp, the artist who controversially first displayed a urinal in a gallery; Man Ray, who invented solarised surrealist photography; and the dada poet Francis Picabia. How and why did these artists become so influential that many would claim they changed the course of art history?