The new head of the intelligence agency, Anne Keast-Butler set the 'trickiest Christmas Challenge so far' for schoolchildren around the country.
GCHQ, the UK's largest intelligence agency, has sent out its annual Christmas card, complete with a set of puzzles aimed at Britain's youngest minds.
Keep your little ones entertained (or highly frustrated) this year with GCHQ's festive brain teaser that puts your analytical and mathematical skills to the ...