The spies’ American neighbours were stunned when the FBI arrested them as part of a roundup of Russian operatives in 2010. One young neighbour was incredulous: ‘“They couldn’t have been spies,” she said jokingly. “Look what she did with the hydrangeas.”’ Two matters stand out about the case. The Russian spies had been planted in the suburban soil of the United States to report home on news that could just as easily, in most cases, have been pulled from the internet. And then, too, they were astonishingly well trained and equipped for what seems so frivolous an enterprise. As the New York Times reported, the group ‘had everything it needed for world-class espionage: excellent training, cutting-edge gadgetry, deep knowledge of American culture and meticulously constructed cover stories’. And that is why the hydrangeas were important. Whether the Russian denizens of that particular house were simply avid gardeners or had been trained in the ways of American suburban horticulture, they looked like they belonged. It takes craft for a spy to blend in. Without that craft, there is no espionage.

Espionage is said to be more art than science. And as the world’s second oldest profession, it is an ancient and practised art. The tricks of its trade are so well established that, as one British veteran claims, ‘There are no new ways of collecting intelligence.’ Another old Asia hand notes that although the tools have grown more sophisticated, the principles of espionage are essentially the same today as they were between the World Wars. He explains that ‘The steamship is to the navy as tradecraft is to espionage.’ Whether in a calm sea or stormy sea, the principle is the same: the boat must get from Point A to Point B. In order to do this, the captain must know the vessel, just as the officer must know the agent. For all the technical developments that have aided intelligence collection over the last century, one basic element remains the same: people. The psychology of agent handling, including an understanding of human motivations and an ability to manipulate and even control, has been a fundamental part of tradecraft. ‘As long as emotional needs and frailties exist, so will spies,’ one former KGB officer has written.

Sources and methods remain the most closely guarded secrets of intelligence services, for these form the base of all espionage.