Secret service workers are rarely encumbered by vodka martinis, fast cars and pens that fire missiles. Most are humble researchers, who do all their snooping in libraries. Some monitor the foreign media, checking on television broadcasts, books and also the press. Others analyze messages from other countries, and turn them into concise intelligence reports. The messages come from spies; comparatively glamorous kinds, who use espionage techniques to collect intelligence.

They might steal or purchase information, or befriend people with access to it and wait for them to talk indiscreetly. A few of them even blackmail people into co-operating. There are two types of spy. Legal’s work in embassies – they have diplomatic immunity from prosecution, and are merely sent home if they’re caught. They might operate in a specialist field. Military attaches consult with their hosts’ armed forces, which enables them to visit – and spy on! – Army bases. Commercial attaches do the same job in company and industry.

Illegal’s spy on their personal state for a foreign power. They might spy for excitement, for cash, or for a cause – and they risk severe punishment. Intelligence forces such as MI6 and America’s Central Intelligence Agency (CIA) operate worldwide networks of illegals – but there’s an additional kind of agency that works within its own nation, hunting for other countries’ spies.

These counter intelligence forces include Britain’s MIS and the USA’s Federal Bureau of Investigation (FBI). Human spies collect human intelligence (HUMINT), but information can be collected by other means. Spy planes use radar to obtain electronic intelligence (ELINT), and tape communications intelligence (COMINT) from radio waves, although satellites gather imagery intelligence (IMINT) by taking photographs from space! But science can’t do everything. In 1990, intelligence forces failed to predict Saddam Hussein’s invasion of Kuwait – largely because they didn’t have enough human agents ‘on the ground’ to judge the mood in Iraq.