I enjoyed reading this book, there was a sense of anticipation which made you want to keep reading to find out what happened. It was great to introduce kids to Bletchley Park, I'm sure a lot of people will be interested in finding out more about it after reading this book, but it struck me as unlikely that children would be allowed to work and sign the official secrets act (they may well have done, but I'm not sure!). I felt some of the storyline needed explaining a bit more than it was, especially at the end, as it left me a bit confused over who was a good guy and who was a bad guy. There were a lot of references to nature in it, and it was nice to have the 3 children having different interests, but (mostly) accepting each other and encouraging their passions. Not sure Robyn would have been in a good state after swimming in a lake in February, maybe that shouldn't be encouraged, but a good read all in all.