The Grove of Eagles is a 1963 historical novel by the British writer Winston Graham.Stade & Karbiener p.209 It is set in Cornwall during the Elizabethan era around the time of the Spanish Armada. The period was of particular interest to Graham and he wrote a non-fiction book The Spanish Armadas in 1972.
References
Bibliography George Stade & Karen Karbiener. Encyclopedia of British Writers, 1800 to the Present, Volume 2. 2010.