If you think you’re good at puzzles, you should probably test yourself on this complex brain teaser created by the UK’s largest spy agency. The GCHQ sent out its annual Christmas card this year complete with a puzzle that’s certainly a head-scratcher. To solve the puzzle, you’ll have to complete a series of letter sequences and then fill in your answers in the Christmas bauble image featured on the front of the card.

The instructions read: “Complete the following nine sequences and plot your single-letter answers in the corresponding golden nodes on the bauble. Follow the flow of the arrows from somewhere frosty to unlock a message.”

To play along at home, the sequences are: GFEDCB_; NOHHPQ_; MDCLXV_; POIUYT_; DPLLMS_; HHELIB_; NAMWON_; EOEREX_; and GMRDPR_.

uk space agency christmas card puzzle

Photo: GCHQ

The answer will be posted on the GCHQ website and Twitter account, which also publishes new puzzles on a weekly basis.

According to a GCHQ spokesperson, “Problem solving is at the heart of what we do. Taking on this Christmas cracker gives puzzlers an insight into the skills you need to be a GCHQ analyst. Bring together a mix of minds by sharing it with the wise men and women in your household to find the solution.”

GCHQ is perhaps most famous for its actions during World War II and its legendary codebreaker Alan Turing who developed the Enigma machine to decrypt coded German messages.