Ah, I should have checked it.
Walker created the slogan "Trill makes budgies bounce with health" - a famous advertising slogan for bird seed in the 1960s as well as the slogan "Opal Fruits, made to make your mouth water."
But it doesn't state his position.
So he was a copywriter?
He was indeed. Another budgie ad (ironic, considering his later collaboration with James Hunt, who had a "light green cock" according to the IPC publication Cage & Aviary Birds) had the slogan "An only budgie is a lonely budgie", cunningly urging people to get an extra dumb bird and thus double their Trill consumption.
He also did, "A MARS a day helps you work, rest and play", thus proving conclusively that he was already at the head of the field, as far as talking b*****ks is concerned.