How fact met fiction in Le Carré's secret world

The tweet from the current chief of MI6 paying tribute to his "evocative and brilliant" novels would have raised a wry smile from John le Carré. The writer's relationship with his former colleagues was always deeply complicated - as has been their attitude towards him.

Le Carré's career was shaped by his time in the secret world and, in turn, his own fiction shaped the way much of the world saw British intelligence, including the way even spies talked about themselves.

Writers often draw on real life experience but because le Carré's experience was inside a world that was secret - and much more secret in his time than today - it is particularly hard to know where fact ends and fiction begins, creating a mystery whose value he understood.