Gideon may or may not have overcome the Midianites by superior intelligence. The Book of Judges is a little obscure about that. But there is still something in the old adage that espionage is the second oldest profession. The rules of the game were set out more than six centuries ago in the advice given by one of his councillors to a king of France. Pay your spies well. Never let one of them know about the others. And don’t believe everything that they tell you. It is a good starting point, even today.

Yet the profession is dying, progressively bypassed by electronic eavesdropping and satellite photography, and super- seded by computerised analysis. The trend is very ancient. Intercepted communications, whether they were radio signals or coded letters sewn into a horseman’s jacket, have been the main source of intelligence for centuries. Spies played a colourful part in the wars of the 20th century, but an essentially insignificant one. It is difficult to think of a single notable event of modern times whose course has been changed by information derived from spies.

It is not just technical advance that has killed off HUMINT (human intelligence). With a handful of exceptions, old-fashioned spies are unreliable. It is largely a problem of motivation. Spies are usually natives of the country being spied on, who do what they do for money, grudges or self-importance, all instincts that tend to distort the message. They exaggerate to earn their pay. They make things up to forward their own agenda. They get caught and turned, becoming channels for deliberate misinformation.

Blackwell Bookshop

Purchase your copy here, 10% off RRP