Simpson was born in London in 1782 and was a student at the Royal Academy and for some years an assistant to Sir Thomas Lawrence, PRA.
Late 19th-century biographer Sidney Lee was of the opinion that Simpson was "rather a skillful portraitist than an artist and that his portraits are not without power, but lack instinct and penetration."
Simpson's painting The Captive Slave was acquired by the Art Institute of Chicago in 2008 — it had not been displayed to the public for 180 years.
[1] Reviewer Martin Postle concludes:Despite enduring critical neglect and eventual obscurity, Simpson was a gifted artist, capable at times of venturing beyond the parameters of society portraiture and his position as a studio assistant.
And in one particular work, The Captive Slave, John Simpson produced a painting of iconic status, which can be regarded today as his masterpiece and as a worthy emblem of the aims and achievements of the Abolition Movement.