 She was a cousin of Eric Gill and sister of Colin Gill.She was educated at Bedales School and University College, Reading, where she took a diploma course in horticulture.In 1921 she married Clifford Allen, a leading member of the Independent Labour Party who had been imprisoned as a conscientious objector in World War I. Marjory Allen worked as a landscape architect throughout the 1920s and 1930s and was elected the first fellow of the Institute of Landscape Architects in 1930.