Image source, Getty Images

By Jacqueline Howard

BBC News

What do gift tags, candy canes and several layers of hardened code have in common?

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

Ensuring sharp minds do not fall idle as the winter break approaches, GCHQ has released its code-breaking challenge, aimed at 11 to 18-year-olds.

More than 1,000 secondary schools signed up for the 2023 event, which this year features some of the trickiest puzzles yet.

This is the third edition of the challenge, which is designed around a Christmas card sent by Anne Keast-Butler, the director of the Cheltenham-based intelligence agency.

Challenges enclosed in the card are designed to test skills such as codebreaking, maths and analysis and each is designed to be harder than the last.

Let's ease ourselves in with one of the (apparently) less demanding questions.

Image source, GCHQ Image caption,

Can you solve this puzzle?