brainteaser

The annual brainteaser aims to tickle the neurons of those hoping to work in intelligence, and comes in the form of a Christmas card, sent by the national spy agency's director Anne Keast-Butler.

GCHQ's annual brainteaser comes in the form of the agency's Christmas card, sent by the intelligence organisation's director Anne Keast-Butler.

For the more numerically minded, the next brainteaser may be more appealing...

They are all elements of an annual brainteaser for UK school children set by the nation's spy agency.

It is less about creating the perfect brainteaser and more about showcasing a flawed family with outsize personalities.