He started playing the trombone at age 11 and by 1966 he had joined the New Welsh Jazz Orchestra. In that period he first joined the Graham Collier Sextet. In 1968 at the Barry school he worked with Keith Tippett and became a founding member of his sextet. He later worked with South African band Brotherhood of Breath and also Soft Machine. He is an important figure in the Canterbury Scene.
Evans also appeared on the album Lizard by the progressive rock band, King Crimson, in 1970.