LONDON (AP) — A resounding thump breaks the silence as Julia Land drops a lump of grey-brown clay onto the slab roller before Ned Heywood cranks it through the machine once, twice, three times, creating a rectangle about an inch thick. Laying a pattern on top of the slab, Heywood slices through the clay to create a disc the size of an extra-large pizza that will become one of the blue plaques that dot the walls of buildings throughout London, marking the places where scientists, artists, politicians and activists have made history. As English Heritage prepares to unveil its 1,000th blue plaque on Tuesday, the charity is working to broaden the program to include more women, people from minority ethnic backgrounds and community groups so that it better reflects the diversity of the capital.