The Karla Trilogy is John le Carré’s three-novel account of a long duel between George Smiley of British intelligence and Karla, the Soviet officer who runs his own directorate inside Moscow Centre. The books are written in sequence. Each one opens on the damage left by the one before.

Tinker Tailor Soldier Spy (1974) finds Smiley forced out of the Circus after a failed operation in Czechoslovakia. Oliver Lacon of the Cabinet Office brings him back in secret to find a Soviet mole placed at the top of the service years earlier. Smiley works from stolen files, old colleagues and his own memory. The traitor he exposes was recruited and run by Karla, and he is someone Smiley knows well.

The Honourable Schoolboy (1977) puts Smiley in charge of a gutted Circus with almost no staff and no money. He goes back over the intelligence the mole buried and finds a money trail Karla wanted hidden. Jerry Westerby, a reporter and part-time agent, is sent to Hong Kong and across a collapsing Indochina to follow it. The operation works for London. It costs Westerby everything, and the Americans take the prize.

Smiley’s People (1979) begins with the murder of an old émigré agent on Hampstead Heath. Smiley, retired again, is asked to close the file quietly. He follows the dead man’s last lead instead, through Hamburg and Switzerland, and finds the one private weakness Karla has. Smiley uses it. The book ends at a crossing point on the Berlin Wall.

Le Carré served in MI5 and MI6 before the success of The Spy Who Came in from the Cold (1963) let him write full time. The mole plot in the first book draws on the Cambridge spy ring, and Kim Philby in particular. Much of the trilogy’s jargon, such as “mole,” “lamplighters” and “scalphunters,” came from le Carré and later entered real use.