Donald Eric Harley was born in London and studied at Epsom College of Art, where Frank Hampson visited to give a talk about the Eagle and Dan Dare. Harley soon applied for and got a job in Hampson's studio. He was the backbone of the strip, especially during Hampson's periods of illness, and worked with Hampson, Eric Eden and Joan Porter until the studio was disbanded in 1959 after Odhams Press took over the paper.
He remained on the strip for a time, drawing the second page while Frank Bellamy did the first, from scripts by Eden. After a year Bellamy left the strip and Harley became the lead artist, assisted by Bruce Cornwell, until 1962 when a new team of writer David Motton and artist Keith Watson took over. He later drew "Thunderbirds" in Countdown (1971-72), and worked in nursery comics in the 1980s.