Hart's break into broadcast television work came in 1952, after his brother persuaded him to attend a party where he met a BBC children's TV producer. After an interview, in which Hart drew a fish on a napkin while the producer was looking for paper, Hart became resident artist on the "Saturday Special" programme. Subsequent TV shows included "Playbox" (1954–59), "Tich and Quackers", "Vision On" (1964–76) "Take Hart" (1977–83), "Hartbeat" (1984–93), "Artbox Bunch" (1995–96) and "Smart Hart" (1999–2000). From the 1970s, he often appeared alongside the animated Plasticine stop-motion character Morph, created by Peter Lord of Aardman Animations.