Original sentence: After her marriage to Herbert Spencer Clark, the couple continued to reside in the mansion, and there fostered the arts, turning the home into a museum, so that by the time of the Second World War, it had became The Guild of All Arts
Edited sentence: After her marriage to Herbert Spencer Clark, the couple continued to reside in the mansion, and there fostered the arts, turning the home into a museum, so that by the time of the Second World War it had became The Guild of All Arts