Marcel Duchamp is considered one of the great artists of the 20th century, but was his greatest achievement - Fountain - a urinal bearing the signature R. Mutt, the work of someone else? The original Fountain has long been lost, and for many decades forgotten, but in the 1950's became such a talking point again that Duchamp decided to manufacture up to a possible 17 copies - one of which stands proud, under glass, in the Tate Modern. Earlier this century a poll of 500 art historians voted it the most significant art work of the 20th century, for the questions it raises about art and the artist, but although the importance of 'Fountain' in the history of art is undisputed, is it certain the artist was, in fact, Duchamp? And if it wasn't him, then who was it? Join the dots, and the paint brush of history seems to point at the Baroness Elsa von Freytag-Loringhoven - a truly free spirit and radical artist, who Duchamp called 'the future'. The smoking gun is a letter written in 1917 by Duchamp to his sister Suzanne, stating "One of my female friends" had submitted the urinal as a sculpture to the exhibition, "the pseudonym Richard Mutt". True, false, or just a fascinating theory... its one that throws an interesting light over one of the most significant works of the 20th century. Steve Punt dons galoshes and heads for the nearest convenience. Producer: Sara Jane Hall.