The popularity of Blake's powerful and fanciful illuminated printings for his major works has obscured his virtues in working with more mundane subjects. This reproduction of his engraving of the poet William Cowper (1804) shows his skill in this field. In addition to this engraved portrait, Blake provided five other plates to illustrate Hayley's biography.

Although Blake was greatly indebted to Hayley for commissions, advances, and encouragement, his relationship with his benefactor became strained over time. In 1803 he complained to his brother James, "[Hayley] thinks to turn me into a Portrait Painter as he did Poor Romney, but this he nor all the devils in hell will never do."

On the other side, Hayley said of Blake: "This poor man with an admirable quickness of apprehension & with uncommon powers of mind, as often appeared to me on the verge of Insanity. . . ."