Exactly 20 years ago this month, I attended the first on-the-record press conference given by the heads of MI6 and GCHQ. This was quite a moment. Until 1989, the existence of these organisations was not even officially acknowledged; yet here were Sir Colin McColl of the Secret Intelligence Service (MI6) and Sir John Adye, chief of the even more hush-hush eavesdropping station at Cheltenham, prepared to answer questions about what they did.