I've just finished re-reading this, and it's just as good the second time around. Victor Maskell is one of Banville's typically arch, aloof narrators.
The novel is based on the story of the Cambridge Five. Maskell is a thinly veiled Anthony Blunt, with the charismatic Boy Bannister being a perfect reproduction of Guy Burgess, even down to the direct use of quotes attributed to Burgess at the time.
McNeil, the British Deputy Foreign Minister advised Burgess to avoid "the race thing, contact with the radical element, and homosexual adventuring." Burgess replied, "Oh, you mean I shouldn't make a pass at Paul Robeson?"