Code breaker Alan Turing's notebook is set to hit the auction block.

The 56-page manuscript, featuring notes about mathematics and computer science, will be sold at Bonhams auction house in New York in April (15), and is expected to go under the hammer for at least seven figures, with a portion of the proceeds benefiting charity.

Turing was a British mathematician who cracked Germany's wartime communications code, bringing an early end to World War Two.

The notebook has never been seen in public and dates back to 1942.

Benedict Cumberbatch portrays Turing in Oscar-nominated film The Imitation Game.