In 1952 his mother remarried Peter Pettit, the solicitor who had handled her divorce. Bell was educated at Osidge Primary School and Queen Elizabeth's Grammar School, Barnet, and joined ABC Television at 18 as a post boy. He worked in various advertising/PR firms in the late 60s including the London agency Colman Prentice & Varley and later Geers Gross, before helping to found and becoming managing director of Saatchi and Saatchi in 1970, later serving as chairman and managing director of Saatchi and Saatchi Compton from 1975.