Reading and writing secret messages was once impossible for blind people. In the early 1800s, Louis Braille of France invented a system for reading raised dots on a page by using the fingertips. Reading and writing using Braille has been used ever since by people unable to see a printed page.

Blinded soldiers returning from war were often unable to learn or use Braille, particularly if their hands were damaged. Reading Braille needs very sensitive fingers.

Other ways of reading using touch were tried. Ordinary letters of the alphabet raised on the page need to be very large to be felt properly, which causes slow reading speeds and very bulky books.

In the 1840s, a blind Englishman called Dr William Moon invented another system of raised shapes. The letters are made up of lines and curves, similar to the printed alphabet. These shapes are rotated or reflected to create the 26 letters of the alphabet, with dots added for punctuation marks and numbers. The system is now just called Moon, after its inventor.

As the characters are fairly large and many resemble the normal printed alphabet, Moon has been particularly suitable for those who lose their sight later in life, or for people who may have a less keen sense of touch.

The UK-based charity RNIB (Royal National Institute of Blind People) has produced many materials written in Moon.

In case you struggled to decipher the message written in Moon font in the story, or if you want to check whether you worked it all out, the letter to Freddy said this: