Richard Dadd is remembered today for the mysterious and magical fairy paintings produced after his tumultuous descent into the realms of madness and insanity. 
Richard Dadd's early paintings were of landscape, marine and animal subjects. He entered the Royal Academy Schools in 1837 and became a founder member of a group of artists known as 'The Clique'. 

In 1842 Dadd traveled to the Middle East with his patron, Sir Thomas Phillips. The exhilaration of the journey was such that Dadd already doubted his own sanity on his return to London. He entered the competition for the decoration of the Houses of Parliament, but after his design was rejected his mental health deteriorated, resulting in the murder of his father in August 1843. 

Dadd fled to France but was arrested and admitted to Bethlem Hospital. His schizophrenia was recognised and he was extremely fortunate in being attended by sympathetic doctors who encouraged him to paint. Isolated from the world outside and from new developments in art, he fell back upon the themes of his sane period, historical and literary subjects, portraits and fairies. 

Dadd's most extraordinary achievement is the enigmatic The Fairy Feller's Master Stroke (1855-64), a hallucinatory vision of fantastic creatures, seen as if with a magnifying glass through a delicate network of grasses and flowers. All are watching the fairy woodman (or 'feller') aiming his axe at a hazelnut, a moment pregnant with never-to-be-explained significance. 

Dadd spent the last 22 years of his life at Broadmoor Hospital for the Criminally Insane where he died in 1886. 

Source: http://artmagick.com/artists/dadd1.asp