(Daldinia concentrica)
This is a saprobic fungus, which breaks down dead wood. It's mainly found of Ash and Beech; occasionally on other hardwood species. The hard fruiting body can live for year and, when cut open, you can see growth rings like those that can be seen in the cross section of a tree.
Younger fruiting bodies are pale and they darken as they age. The common name, King Alfred's Cake, originates from the story that King Alfred was given refuge by a peasant women. He was left watching her cakes baking but forgot about them and left them to burn. They're also known as Cramp Balls, as it was believed that carrying them would prevent cramp, and Coal Fungus, due to their likeness to lumps of coal.
Daldinia concentrica is an excellent natural tinder. Once ignited with a spark, they will smoulder for a long time and can be used to transport fire from one location to another.
King Alfred's Cake is one of the dead wood species that is introduced in 'The Tree That Held The Moon' to inspire curiosity in the wonders of nature.