Our partners at GCHQ have been with us from the start at CCHQ (cipher challenge hq for the avoidance of doubt) and we are extremely grateful to them for their support. Some of you may already know that they run a variety of challenges of their own including the weekly puzzle, which you can find on Twitter at #GCHQPuzzle, and their annual Christmas challenge, which starts on December 11th. You can read more about it at https://www.gchq.gov.uk/news/christmas-challenge-2024.
Have fun!