MI6 suffered a rough patch after intelligence that the agency provided for the Government’s infamous dossier on Iraq’s weapons of mass destruction (WMD) turned out to be unreliable at best and unproven at worst.

Intelligence is its business and if the product is suspect, reputations can be severely damaged. Despite the dossier, however — and MI6 was hardly alone in believing that Saddam Hussein was hiding his WMD arsenal — the 2,000 inhabitants of one of the most exotic buildings in London, Vauxhall Cross, have managed to restore their standing in Whitehall and overseas.

Sir John Scarlett, the quietly spoken incumbent chief, introduced a tough agent-vetting system after he took over in 2004 to ensure that secret intelligence came from bona fide sources and not, as in the case of Iraq, from people with an agenda to bring down Saddam.

Unlike the CIA and the rest of the vast American intelligence apparatus, MI6 is a relatively small organisation. Its reputation relies for the most part on the ability of its officers posted abroad under diplomatic cover to find human intelligence sources (humint).

This entails running networks of agents who can supply genuinely secret information — not cocktail party tittle-tattle or plagiarised versions of foreign newspaper articles but highly classified intelligence upon which the British Government can partly base its foreign and security policy objectives.

Sir John Sawers, as the new “C” from November, has the prospect of facing a rising threat from international terrorism and a nuclear-armed Iran during his five years in office, and he will need to decide where best to deploy his intelligence officers. The key stations will still include Islamabad and Kabul because of the British troop commitment in Afghanistan and the threat from al-Qaeda-supporting British Pakistanis intent on launching terrorist attacks in Britain.

However, there are many other parts of the world where it will become increasingly important for MI6 officers to gather high-class intelligence. With al-Qaeda franchises popping up in unstable nations, it’s likely that a growing number of intelligence officers will have to be deployed to officially defined “hotspots”.

Spying has always been a potentially dangerous business but the world is becoming more unpredictable and it will be the job of Sir John Sawers’s men and women to warn of events before they happen.

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