Black Hole
May contain traces of nut
The Turing Challenge
Try our toughest puzzle to celebrate Alan Turing featuring on the £50 banknote
www.gchq.gov.uk
The puzzles are based on the unique design elements of the new banknote, such as the technical drawings for the British Bombe, the machine designed by Turing to break Enigma-enciphered messages during WWII. GCHQ puzzlers say the full challenge could take an experienced puzzler seven hours to complete.
Good luck with that...