He played PC Dave Litten in 12 episodes of "The Bill" between 1984 and 1986 (as well as the 1983 pilot episode, "Woodentop"). Olsen also starred in the 1986 TV series Prospects alongside Brian Bovell who played Jez Littlewood in "Gimme Gimme Gimme", about two friends living in the Docklands area trying their hand at anything to make a "few bob". In 1988, he appeared in the "EastEnders" spin-off "CivvyStreet" as Albert, the patriarch of the Beale family. His most prominent role was as Ben Porter in "2point4 Children" (1991–1999). He also had leading roles in another two short-lived BBC sitcoms "Health and Efficiency" (1993–1995) and "Pilgrim's Rest" opposite Gwen Taylor for one series in 1997. From 1999–2000 he played Johno in the Daz Dogs adverts and sponsors.