Knowels began studying art and music at Kelly College. His father attempted to make him into an agricultural estate agent, but Knowles refused. He instead got into advertising, and while working for a soap company was sent to Africa where he discovered tribal art. Knowels became fascinated with this tyep of art and began collecting African art as a member of the Royal Anthropological Society. He later moved to New York and started painting full time. His work is known for its limited color, shaped canvases and free-standing shapes to create "lyrical" paintings. In sculpture, he experimented with a variety of materials. Knowles has been featured in high profile shows including at National Technical Museum in Prague, at Austin/Desmond Fine Art in London, at Lemon Street Gallery in Truro, at the Museum and Art Gallery, Plymouth, and Michael Wood Fine Art.