Barbara Hepworth with the plaster prototype for the United Nations Single Form at the Morris Singer foundry, London, May 1963. Photograph by Morgan-Wells. Barbara Hepworth © Bowness

Barbara Hepworth with the plaster prototype for the United Nations Single Form at the Morris Singer foundry, London, May 1963. Photograph by Morgan-Wells. Barbara Hepworth © Bowness

Barbara Hepworth with the plaster prototype for the United Nations Single Form at the Morris Singer foundry, London, May 1963. Photograph by Morgan-Wells. Barbara Hepworth © Bowness