In Tinker Tailor Soldier Spy, he is approached by Smiley regarding information concerning the betrayal of Jim Prideaux on an assignment in Czechoslovakia.
In The Honourable Schoolboy, Westerby is recalled from his semi-retirement in Italy and despatched to Hong Kong, in an effort to flush out a deep-cover Soviet spy in China.
Westerby was played by Joss Ackland in the 1979 television adaptation of Tinker Tailor Soldier Spy.
[5] Played by Stephen Graham in the 2011 film adaptation, his role in the plot was amalgamated with that of Sam Collins from the novel.
[6] Hugh Bonneville played the role of Westerby in the BBC Radio 4 dramatisation of the John le Carré novel The Honourable Schoolboy, first broadcast in January 2010.