There's another pair of John Gardner books going free at Amazon UK today. The first book was free a few years back.
The Secret Houses (Secret Trilogy #2)
The Secret Families (Secret Trilogy #3)
Spoiler:
The Secret Families is the final shattering move in the trilogy, the checkmate from a grand master of espionage.
The year is 1964.
The Cold War is at its height and Caspar Railton, the 'wounded lion' of the Railton clan, which for decades has dominated British Intelligence, is dead.
Even worse, evidence has emerged suggesting Caspar was a traitor and suspicion surrounds not only the Railtons but also the Farthings, the American family of spymasters connected by marriage to their British counterparts.
Yet Naldo refuses to accept his uncle's guilt and is determined to clear both families' names.
With his cousin Arnold Farthing he embarks on a quest to uncover Caspar's past, a mission which takes both men deep into some of the most dangerous territory any agent can enter …
The Secret Families completes John Gardner's The Secret Generations trilogy, which is a giant work of fiction drawn from the dramatic history of Britain’s intelligence and security services.
Through the story of one family, the Railtons, whose lives become caught up in some of the greatest struggles of the twentieth century, Gardner traces the birth, the early clashes, the successes and failures of the organizations now known as M15, M16 and GCHQ.