Hart took after the end of World War II to study art at Maidstone College of Art, which was interrupted by his call-up to the Korean War. After graduating in 1950, he worked as a freelance artist in London. In 1952 he was hired by the BBC for the children's show Saturday Special. Until 2000, he was seen intermittently in various children's programs. He showed in these programs both crafts to follow suit, as well as large picture creations that could be seen only from the air.
Hart was recognized for his work with two BAFTA Awards, including an award for his life's work 1998. 2001 he withdrew into retirement. Two years later, his wife died, with whom he had been married for 50 years. According to an interview with the Times, he had been suffering for years from the effects of two strokes.