Point of interest

Dr. Johnson is famous for having written a pioneering dictionary of the English language. Williamson owned a portrait of him which was sold when he died and, like most of his possessions, has never been traced. A 1984 biography of Johnson lists all his official portraits and accounts for the whereabouts of all of them bar one, painted by a German neo-classical artist called Johann Zoffany. Could the missing portrait be the one that Williamson had on his wall?