Board Thread:Questions and Answers/@comment-194.66.201.10-20151109111740/@comment-30546716-20161130201622

The inscription was probably always intended to be an imaginary language. Merlin's setting is essentially a fantasy world loosely inspired  by history. Its a bit like how Tolkien's written Elvish is based on the Old English script. Hence, the Saxons in series 5 have no resemblance to the Germanic people that arrived in Britain between the fourth and sixth centuries.