For some, the trick was simply to learn to smile more (back home, mirth was in short supply). Others went to greater, more painful lengths to blend in: one man got himself circumcised to pose as a Jew. Why? Because they were Russian spies. Their job was to spend years integrating into the life and customs of their adopted Western country so as to learn its secrets and report back to Moscow. But, as Shaun Walker reveals in The Illegals, a fascinating account of 100 years of deep-cover espionage, while some sleepers did achieve success, particularly in the interwar years, most did not. Either they fell foul of their own paranoia one illegal in Britain became convinced MI5 was bugging his shirt buttons or of the paranoia of the Kremlin, which had them shot or sent to the Gulag on their return home. A former Moscow correspondent for The Guardian, Walker has spent years delving into archives and memoirs and interviewing retired illegals to elicit a wealth of extraordinary material, much of it never before recorded. He has lifted the lid on a very Russian sort of subterfuge.