Colossal heads, with luminous faces – intense and inscrutable – line the walls of Jenny Saville's studio in Oxford, England. She described the portrait's inner glow: "I'll just rub the paint in and make it have a sort of inner light that's left here. It's a special thing that only paint can do actually." And what is it that she hopes to convey? "To distil a sort of essence of what we are as human beings," she replied. "I mean, I think that if you paint figuratively, that's what it's about