Blighty's communications eavesdropping nerve centre GCHQ has issued two papers written by superboffin Alan Turing on the maths behind code-breaking.

The documents, held in secret for 70 years, laid the foundations for the quick and efficient decryption of Nazi Enigma-scrambled messages - a breakthrough that lopped about two years off the duration of the Second World War.

The papers were donated on Friday to The National Archive in Kew, Surrey, where they will be available to view on request. An archives spokesperson said demand to see Turing's work is high, but there is no plan to put it online....