From time to time I attend informal meetings, somewhere in Whitehall, where academics and practitioners get together to discuss matters of intelligence interest. The items may be historic or current, and the participants include elderly veterans from the Second World War as well as far younger men and women who are always charming but studiously evasive about their current jobs. 

On my most recent visit I found myself sitting next to a veteran of Bletchley Park, one of the rapidly diminishing band of legendary code-breakers who cracked open the ciphers of Nazi Germany and its allies, not to mention those of neutral and friendly powers, and thus helped shorten the