Crossley-Holland and The Seeing Stone won the annual Guardian Prize and Tir na n-Og Award.

The obstacles disappear when he learns on his fourteenth birthday that his "uncle" Sir William de Gortanore is really his father; he becomes heir to a large manor.

The novel ends with Arthur accepted as squire to the Lord of the Middle Marches, Stephen de Holt.

The wizard Merlin gives Arthur de Caldicot the "Seeing Stone" early in the story, along with the warning it will cease to work if anyone else shares in its knowledge.

Eventually it becomes clear that King Arthur inhabits a parallel universe, with events in both worlds reflecting each other.

[5] The Seeing Stone was bronze runner up for the Smarties Prize in ages category 9–11 years and it made the 2000 Whitbread Awards children's book shortlist.

[2] There were Danish, Finnish, German, Spanish, and Norwegian-language translations that year; Catalan, French, and Italian in 2002; Hebrew 2004, Serbian 2006, Romanian 2008.