The husband, identified by lawyers in the case as Antonio C, found out about the adultery when he was looking through an old chest of just before Christmas.
The couple are expected to divorce after the betrayal.
He immediately asked his wife, who is identified as Rosa C, for a divorce as he was so upset over the betrayal.
Court papers released in Rome this week revealed that she sent letters to her lover during a secret affair in the 1940s.
The couple have five children, a dozen grandchildren and one great-grand child, but the discovery proved to be the last straw for the marriage, which reportedly ran into trouble ten years ago.