My first year in the Foreign Office, in the days before email, was a deluge of papers: thin, white-coloured memos from other government departments, propelled across Whitehall through Victorian vacuum tubes; letters from MPs, engraved with a portcullis, demanding answers; stiff, pale-blue documents that had the scrawl of a minister across them, approving or rejecting whatever speech or meeting or diplomatic manoeuvre we had most recently recommended.

Most dramatic of all, though, were those that came in coloured folders marked ‘Secret’. These were attended with particular ceremony: handed from person to person, never left unguarded, and often read with particular care. They, being reports from the Secret Intelligence Service, were my introduction to the particular mystique that surrounds anything to do with spying.

The mystique is partly due to the human love of uncovering secrets. From the Greek philosopher Pythagoras, who only allowed his students to meet him face to face after they had proved their discretion through five years of silence, to the bloggers who today accuse the Bilderberg Group of covertly