Lucien Freud's reaction to a nasty altercation with a taxi driver was to get his rather impressive black eye down on canvas. Self-Portrait With a Black Eye, has been largely unknown to the art world for the past 30 years. It has never been recorded in published literature on Freud and never publicly exhibited. Instead, it has remained in the same collection since 1978. Sotheby's estimates the life-size portrait to sell for up to £4m...