The Lost Years by E. V. Thompson
Perys Tremayne is not readily accepted by his family in Heligan, Cornwall, because his late parents had caused a scandal, but neither did he fit easily with the servants. A neighbouring farmer's daughter, Annie, and her brother, Martin, the Tremayne's chauffeur, were the only two who would befriend him. But when war breaks out in 1914, Perys' life picks up - his determination and talent for flying enables him to join the RFC and become a distinguished flying ace. Although his war years and flying career go well, his love life was less successful. He is deeply attracted to Annie, but she has an understanding with Jimmy who returns from the Front blind and gas poisoned so she feels she must go through with her marriage. Perys' next girlfriend is Grace, a nurse, but she's on the S. S. Sultan, torpedoed and sunk by the Germans. When war ends, Perys meets up again with Annie just after Jimmy commits suicide, unable to live a disabled life.