Based on the research I've done it seems Banville did a good job of capturing Anthony Blunt's personality that aided him in his espionage and allowed him to remain undetected: his coldness, his gentlemanly Britishness, his loyalty to his friends. I wonder if Banville chose Blunt to portray because he was such an enigma which made it interesting to pursue the study of him and what his motivations may or may not have been. Lots of layers to his personality and secret lives. The book does a great job on continuing the character's habit of dissembling even in the writing of his memoirs while facing death by illness - certainly an unreliable narrator.
I found this article written about Blunt on the eve of the release of his real memoirs in 2009. It was interesting to compare the known facts of his lives with characters and events from the book. I also found a webpage on BBC dedicated to the Cambridge Spy ring.
http://www.dailymail.co.uk/news/arti...ck-Royals.html
http://www.bbc.co.uk/history/worldwa...spies_01.shtml