K J Hartley 
End of Innocence 

Europe is on the brink of war and a precariously neutral Lisbon is teeming with British, German and Portuguese spies. In this uneasy atmosphere of espionage and political intrigue, Father Michael Harrington, a professor at an ancient college for the education of English clergy, is about to embark on the biggest adventure of his life: a passionate affair with Dona Elisabete, a stunning, free-living outspoken Portugese socialite. Dona Elisabete challenges him in every way and leads him into increasing conflict with his vocation, and his king and country.