Soon after Sewell turned to acting; his first stage role was in "One More River" (1959) at the Duke of York's Theatre in London while his television and film roles included First Waterman in "Nick of the River" (1959), Sam in "Where the Party Ended" (1960), Soho layabout in "No Hiding Place" (1960), and Boxer in "Armchair Theatre" (1960).