When Mr. Clark, the Year 6 teacher, announces that this term every student will be writing a Daily Status report about their life and their hobbies, Joe panics. What can he write about? His life is boring and he has zero hobbies.

But Mr. Clark seems to have the idea that Joe likes making and breaking codes. Result Joe can run with that.

Before he knows it, he's finding out about the Enigma Machine that was famously used by the British to crack German secret codes during World War II.

The trouble is, it's still not enough to fill up a daily status for forty whole days,...