Walker studied in Birmingham. Some of his early work was inspired by abstract expressionism and post-painterly abstraction, and often combined apparetly three-dimensional shapes with "flatter" elements. These pieces are usually rendered in acrylic paint.
Around the early 1970s, Walker made a series of large Blackboard Pieces using chalk and the Juggernaut works which also use dry pigment. From the late 1970s his work makes allusions to earlier painters, such as Francisco Goya, Edouard Manet and Henri Matisse, either through the quoting of a pictorial motif, or the use of a partcular technique. From around this time he began to use oil paint more.
After spending some time in Australia, Walker got a job at the Victoria College of the Arts in Melbourne. He produced the Oceania series around this time which incorporates elements of native Oceanic art.
Walker was nominated for the Turner Prize in 1985.