Big-government secrets require a lot of secret keepers. As of October 2012, almost 5m people in the US have security clearances, with 1.4m at the top secret level or higher, according to the Office of the Director of National Intelligence.

Most of these people do not have access to as much information as Edward Snowden, the former National Security Agency contractor turned leaker, or even Chelsea Manning, the former US army soldier previously known as Bradley who was convicted for giving material to WikiLeaks. But a lot of them do – and that may prove the Achilles heel of government. Keeping secrets is an act of loyalty as much as anything else, and that sort of loyalty is getting harder to find in the younger generations. If the NSA and other intelligence bodies are going to survive in their present form, they are going to have to figure out how to shrink the number of secrets.

As writers such as Charlie Stross have explained, the old way of keeping intelligence secrets was to make it part of a life-long culture. The intelligence world would recruit people early in their careers, and give them jobs for life. It was a private club, one filled with code words and secret knowledge.