Explaining metadata collection with Alan Turing, Theresa May and Winston Churchill

My latest Guardian column is a one-act historical drama about metadata, starring Winston Churchill, Alan Turing and UK Home Secretary Theresa May:

May: Mr Turing and his colleagues have laboured hard with every hour that God has sent, but try as they might, they can extract nothing of use from the Enigma cipher.

Churchill: (roaring) Nothing? All these years, all this work, and you have nothing?

May: Well, not precisely nothing, prime minister. The lads have got far enough that they are able to e...