This is a large fungus (cap to 15 cm) that varies in colour and cap may be saffron, orange or ochre, and is covered in fibres.  The stem has a ring and crowded gills are rust-brown at maturity.  

Other rust-gills are usually smaller 

Photograph from top down, in side-view and gills; indicate size, note habitat and substrate; species of tree it is growing on or under

Typically found growing on tree stumps, logs, or at the base of deciduous trees.

Found from late summer to autumn

Widespread but not particularly common in Britain.

Occasional in Leicestershire and Rutland.

https://www.first-nature.com/fungi/gymnopilus-junonius.php