John Sullivan grew up in Balham, South London, failed his eleven-plus and left school at 15 with no qualifications. From a working-class background, Sullivan's Irish father was a plumber and his mother occasionally worked as a charlady. It was in Balham where he observed the sort of market trader that would later appear in Only Fools and Horses. Sullivan's first paid employment was as a messenger boy for Reuters.
Sullivan got a lot of his material for Only Fools and Horses scripts from his real-life experiences i.e. the chandelier falling, his father's poker sessions, his niece working in the police force, and his grandfather falling down holes to claim money.
On 2 September 2008 John Sullivan was awarded an Honorary Fellowship at Goldsmiths, University of London. He now lives in the city of Brighton and Hove.