Ruskin Spear (1911-1990), Patients waiting outside a first aid post in a factory. Wikimedia Commons Humankind: Ruskin Spear Tanya Harrod, Studies in Art, The Estate of Francis Bacon Publishing and Thames & Hudson, 2022, £35 PHILIP WARD-JACKSON remembers an unpretentious but greatly gifted artist ‘This is not a full-scale biography’ apologizes Harrod, lamenting the dearth…