Those of you who have read Caleb and the Incredible Counting Machine will remember that the final chapters saw Caleb and Grandpa locked in a dungeon in Prince John’s castle – and getting out involved getting hold of various keys!

When I was writing the story, I had to stop and check whether metal keys of the kind I was imagining would have existed in the 12th century, when Prince John lived… What do you think?!

It turns out that the first locks were invented by the Egyptians 4000 years ago. These were made of wood and involved wooden pins falling into slots in a wooded bar (which is the same basic concept most locks still use today!) It was the Romans who used the first metal locks over 2000 years ago. By the time Price John was born in 1166 they were in common use, though the shape of the keys was probably simpler than the ones I showed in the picture.

Activity 1 – Find the Keys

Here is a challenge for those of you who think they have sharp eyes. Can you find all the keys hidden in the picture of Bernard the dungeon keeper taking part in the experiment?

Activity 2 – Dungeon Escape

Caleb had to rely on his memory a few times to find his way from the dungeons to where the camper van was hidden.

See if you can find all the keys you need to get through the doors as you make your way to the finish – and freedom. This is a fiendishly difficult puzzle that will test your memory to the limit!

Note that some of the colours are quite similar, so to distinguish them a bit more the coloured dots are sometimes circles and sometimes diamonds.