Her first film role was in the Italian film "The Devil Is a Woman" (1974) starring Glenda Jackson. Also in 1976, she featured in an episode of "" as Anna Davies in 'Testament of Arkadia'. Harrow played Helen Alderson in the film adaptation of James Herriot's book "All Creatures Great and Small" (1975), starring alongside Simon Ward and Anthony Hopkins. She reprised the role the following year in the sequel "It Shouldn't Happen to a Vet", this time opposite John Alderton and Colin Blakely.