Margaret Lacey was a nanny/housekeeper employed by Ken Barlow two months after the death of his wife Valerie. In the interim, Val's mother Edith Tatlock and several of the neighbours had helped him with Peter and Susan but Ken wanted someone he could trust to discipline as well as spoil them and so he hired Margaret, who had years of experience in the field.
Assuming her responsibilities at 3 Coronation Street, Margaret managed to upset Ena Sharples, Edith and Albert Tatlock with her no-nonsense style, and in Albert's case, restricting his time with the twins as she felt he let them run riot. Margaret was heavy on discipline, with her usual response to bad behaviour being to lock the twins in their room. Ken had no complaints about her conduct although on one occasion she disciplined the twins for scribbling on a book, only for Ken to discover that it had already been scribbled on when he received it from Len Fairclough earlier that day. Her severe parenting style resulted in the twins becoming hard and unruly at school, causing their teacher Mrs Fielding to visit Ken and inform him, however Ken put this down to Val's death.
Ken's new nanny soon caught the attention of Lucille Hewitt, who had spent two years in an orphanage after her mother Lizzie's death in 1959. Soon after meeting Margaret, Lucille realised that she'd known her from the orphanage, where Margaret, as one of the older girls there, had tormented Lucille and other girls her age. Confiding in Elsie Howard, Lucille explained that Margaret, or "Irma Grese" as the girls knew her, helped out the staff at the orphanage and once locked her in a coal shed for half a day. Margaret too recognised Lucille, and met with her to explain herself. Admitting to having been immature and insecure, Margaret offered Lucille a heartfelt apology and asked her to keep her mouth shut as she liked Ken and the twins. Lucille was unmoved by her words, turning down her offer of a coffee and a "cozy old chat about the good old days". Not convinced that Margaret had changed her ways, Lucille made no promise that she would stay silent. A few days later, they had a second, less polite, confrontation, in which Margaret called Lucille bitter and accused her of exaggerating everything in her head.
Lucille made up her mind to tell Ken all about Margaret after learning that Margaret had locked them in their room again on their birthday, this time to calm them down and because Peter had been throwing food around. However, she waited until after the twins' birthday party to avoid spoiling it for them. When the time came, Margaret told Ken herself, her side of the story being that she had no parents and used to take charge at the orphanage. Wanting to prove herself, she was overzealous, and bullied sometimes as young people in authority do. She felt that the experience had helped her into the world from a poor start and noted that she hadn't received any complaints regarding the twins, however Lucille blamed her for driving her out of the orphanage. Feeling that her confession would damage Ken's faith in her, Margaret resigned and left the Street, leaving Lucille wondering if she'd done the right thing.