
1) Author of The Silver Chalice 2) The Silver Chalice author
Found on
https://www.crosswordclues.com/clue/costain

Costain is a surname of English, Scottish and Manx origin. When originating in Scotland and northern Ireland the surname is an Anglicisation of the Gaelic Mac Austain, meaning `son of Austin`. The English surname is a reduced form of Constant or Constantine. ==People named Costain== ...
Found on
http://en.wikipedia.org/wiki/Costain

Costain, Thomas B. The Pageant of England, The Conquerors; Doubleday & Company, Inc.; Garden City, New York, 1949.
Found on
http://www.wordinfo.info/words/index/info/view_unit/4224/

1885–1965, U.S. novelist, historian, and editor, born in Canada.
Found on
https://www.infoplease.com/dictionary/costain
No exact match found.