The book by Harold Plenderleith entitled The Conservation of Antiquities and Works of Art that was published in 1956 was a seminal event for conservators that marked their emergence from the shadows of museum basements into the light of a new profession. Harald Plenderleith, who lived through almost all of the 20th century, witnessed - and fostered - that emergence and his magnum opus played no small part in the metamorphosis. This paper puts the book in the context of Plenderleith's life and career at the British Museum from 1924 until 1959 and then as the director of ICCROM in Rome.