Painter, draughtsman and etcher, Mortimer began his artistic training in London in 1757 with Thomas Hudson. He later studied at the St Martin's Lane Academy and William Shipley's Academy in the Strand, where he became friends with Wilson's pupil, Thomas Jones. In 1765 he was elected a Fellow of the Society of Artists of Great Britain and became its President in 1774. He specialised in Anglo-Saxon more than classical history painting but during the 1770s fashioned a new genre of wild 'banditti' subjects, much influenced by Salvator Rosa. At this time he was also involved in several collaborative ventures with other artists and was employed by Robert Sayer to repaint some of the figures in P163 Meleager and Atalanta. NWD406 is believed to be by him, executed as a record of his alterations. In 1778 Mortimer was elected A.R.A. but he died the following February, after which some of his works were exhibited posthumously at the Royal Academy.
