But just as the image of the upper-class mother needing staff has changed, so has that of the nanny. Nowadays it is more likely to be a harassed mum needing someone to look after the kids while she goes out to work.
The number of nanny agencies has increased dramatically in recent years in line with the increase in working mothers, but despite the strict rules governing childminders, who work for only a few hours a day, there are no such controls for nannies who often live with their employers.
But yesterday calls by a newly-formed pressure group for nannies to be entered into a central register, in the same way as childminders, received a mixed reaction from mothers, nannies and agencies.
The Playpen group, which was launched yesterday, is headed by Cheryl Winton, whose six-week-old baby girl was brain damaged after her nanny shook her. The launch came a day after a registered childminder in Yorkshire was jailed for five years for causing the death of a baby by the same method.
Mrs Winton said yesterday that she wanted to rectify the fact there were "no rules whatsoever" governing the employment of nannies. "There are no legal controls because it is meant to be a private agreement," she said. "We want new laws to control nanny agencies and make sure they are subject to the same checks as childminders."
The Norland Nursery Training College has been running its own such register for a number of years. Deputy principal Kay Crosse said that its stringent controls had proved invaluable for both parents and nannies. "The register means that Norland Nannies are accountable for their professional actions throughout their career," she said. "We do call our former students back to college on some occasions. Sometimes that's as a support."
Ms Crosse believed the register had made a difference in quality. "If one is brought in, I think it should be a statutory government agency. The difficulty is in catering for a much larger number ... but hopefully where there is a will there is a way."
At present, many parents place advertisements and go through an exhaustive series of interviews to determine a prospective nanny's suitability. Working mother Carolyn Cohn, from north London, said she would have welcomed any information that made finding a nanny easier.
"I placed an ad in The Lady and interviewed lots of people. We did ask lots of questions, but I suspect we didn't ask a lot that we should have done," she said. "We did check out references, but I've heard stories about nannies who gave telephone references and then got their family to make them up. It's very stressful as you are dealing with an unknown quantity."
Mrs Cohn was lucky. Her nanny, Lisa Gray, from Hertfordshire, has now been with her for five years. Ms Gray said yesterday that she could see no reason why nannies weren't registered "as childminders are, and nannies have just as responsible a job". She welcomed anything that would bypass nanny agencies. "Some of them are suspicious of everybody, they give you a real grilling. I can understand why, but a central register might avoid some of that."
A straw poll of nannies out and about with their charges yesterday tended to take the opposite view, however. "I don't think there is any point," said Rebecca Bowers. "The existing system seems to work fine. My employers sat me down with a list of questions and checked out my references themselves. That way people know that they are done properly. If I was going to get a nanny, I would certainly do it myself."
Vicky Clancy added: "I don't think a register would make any difference - after all, that childminder was registered and look what happened."
"Every time something like this happens, there is a big panic, and it is stupid," said Anita Munnelly. "The mums only think about the bad cases and worry even more. If you look around you, the vast majority of nannies are brilliant."