Brian Trueman began his acting career in BBC radio, where his best known work was as a semi-regular member of the cast of the situation comedy 'The Clitheroe Kid'. He first appeared in the show in two broadcasts during the 1957 pilot series, and continued making appearances until the 16th series in 1972. Beginning in one-off roles, after 1965 he was cast as Liverpudlian neighbour Harry Whittle, in which recurring role he continued for the following 7 years. He also became the show's Announcer during its final years on the air.

Prior to 1975 he was principally a radio actor, accumulating 20 years experience of voice acting, which he would put to good use in his subsequent television career between 1976 and 2015, specialising as a voice actor. He gradually moved into television after 1975, initially in acting roles, specialising in character parts and accents, and spending most of his television career in children's television, doing voice acting in cartoons.

He gradually became a scriptwriter for the shows he worked on, writing some of the scripts whilst doing the voices in other episodes of the same show, beginning in the mid 1970s with 'Chorlton and the Wheelies' and 'Jamie and the Magic Torch'; then writing all 43 episodes of 'Wind in the Willows' during the 1980s; and in the 1980s and 1990s writing and performing in 'Count Duckula' and - in his most famous role - 'Danger Mouse', for which he wrote fully 79 of the episodes.

He has written for and voiced many other cartoons since 1980, including 'Budgie the Little Helicopter', and 'Thomas and Friends' (based on the Thomas the Tank-engine stories. In all, he has written over two hundred scripts, for 23 different TV shows, over the period 1976 to 2015, frequently both performing the voices and writing the scripts.