It is popular with adults who lose sight later in life and lack the sensitivity in their fingers to use braille.

Research at the University of Birmingham in the 1990s showed that Moon could also be used successfully with visually impaired young people with additional learning difficulties, because the characters are larger and easier to decipher. Sighted family and friends also find Moon easier to learn, so that reading with a visually impaired child can become a shared activity. As well as introducing children to literacy, the tactile letters help them gain independence when they are able to recognise their name in Moon, for example, and find labelled personal belongings.

There are disadvantages to Moon: it is expensive to reproduce, although new technologies are reducing the cost. The books also tend to be bulky and heavy and the range of reading materials is still limited. However, teachers at Linden Lodge School in Wimbledon, south-west London, believe there are many benefits to the system and are developing ways of teaching the code through the use of mnemonics, and resources such as the Moon Cats reading scheme. They are also adapting children’s books for use with Moon.

Last month, the school launched a website providing information on all aspects of Moon. Pupils from the school are also featured in a handbook and training DVD, Routes to Literacy, published by the Visual Impairment Centre for Teaching and Research at the University of Birmingham. It points out: “There is nothing magical about Moon itself. It is simply a tactile medium that can help people who may otherwise have no access to literacy engage with the written word: a basic right of every individual.”

* Routes to Literacy is available from VICTAR, School of Education, Edgbaston, Birmingham B15 2TT, pound;20. Please specify video or DVD www.moonliteracy.org.uk