Witherop studied at the Liverpool School of Art (1924-30) and received a scholarship to the Royal College of Art (1930-3) where he studied under Sir William Rothenstein (1872 - 1945) and Malcolm Osborne. He won a travelling scholarship to Rome and engaged in restoration work at the Vatican studio. Witherop was particularly attracted to Cornish harbours and rented a studio in St. Ives (1936 -1939) before returning to Liverpool to work for the Air Ministry during World War Two. Witherop also produced many views of Liverpool and the surrounding areas and partcipated in the "Recording Merseyside" exhibitions displayed at the Bluecoat Chambers in Liverpool shortly after the War. Works from these exhibitions were purchased by the Walker Art Gallery and the Liverpool Library amongst others. Witherop later taught at Liverpool School of Art and was also involved in restoration at the Walker Art Gallery, exhibiting at the Royal Academy, Liverpool Autumn Exhibitions and elsewhere in Britain throughout his career.