She has already played a central role in helping her daughter to prepare for the birth of her son, and Carole Middleton will play a uniquely influential part in the upbringing of the future monarch as the Duke and Duchess of Cambridge break with royal tradition.
The couple, who spent most of last week staying with the Middletons in Berkshire, are expected to return there with their son in the coming days, rather than retiring to one of the royal palaces.
Not only that, but friends have said the Duchess does not intend to hire a fulltime nanny, meaning her mother will be relied upon heavily to help out during the baby's childhood.
Penny Junor, author of biographies of the Prince of Wales and the Duke of Cambridge, said Middleton would be a "hugely important" figure in the life of the baby.
She said: "Kate is very close to Carole and an awful lot of young women, when they have had a baby, like being with their mum. I suspect that William not only approves of that idea, but may even be driving it.
"He clearly adores the Middletons, I think he has looked at the Middleton model and seen what a happy family they are, how united they are and how they have fun together, and he would like to reproduce that."
The Duke, whose mother, Diana, died when he was 15, made it clear from the moment the couple first became engaged that the Middletons would not be airbrushed out of the picture.
Aware that his own mother had felt isolated and struggled to cope when she was sucked into the royal machine after her own marriage, he wanted the Duchess to be able to turn to her own family for support, and has been as good as his word. The couple have spent Christmas with the Middletons, they have been on holiday with them, and the Duchess has the freedom to visit her parents whenever she wants.
Now Carole Middleton is preparing to be the sort of hands-on grandmother that has been notably absent from previous generations of royal babies.
Despite their mother's desire to give her sons the most normal upbringing possible, Princes William and Harry had a self-contained nursery at Kensington Palace and a succession of nannies. The young Prince William grew so close to his first nanny, Barbara Barnes, whom he saw more than his parents, that Diana dismissed her when William was 4.
The Duchess of Cambridge, unlike her husband, never had a nanny, and does not share the expectation of other members of the royal family that fulltime nannies are an inevitable part of royal life.
She is expected to spend part of her time during the coming weeks at Kensington Palace, the couple's London home, but is likely to stay with her parents for several weeks once the Duke of Cambridge returns to his RAF base after two weeks' paternity leave. The Queen will leave for her annual summer break at Balmoral on Saturday, and is expected to see the baby before she goes.
The Prince of Wales is in Yorkshire today and Wales tomorrow, meaning it may be Friday, after he completes an engagement in Gloucestershire, before he sees his first grandchild. Prince Harry is with his Apache helicopter squadron at Wattisham airfield in Suffolk and will have to wait until he has a day off before he sees his little nephew.
The Duke and Duchess of Cambridge will face upheaval in their domestic arrangements, because the Duke will finish his three-year tour of duty with RAF Search and Rescue in September. He will not stay on for a further tour at the base, so the couple will have to leave their rented farmhouse, and their next choice of home will be dependent on the Duke's next career move.
He could remain in the RAF but redeploy to another base; transfer to another branch of the armed forces or take on fulltime royal duties. The fact that the couple are keen to give their son as normal an upbringing as possible suggests that the Duke may choose to remain in the armed forces so that he has a fulltime job as he brings up his baby, rather than dedicate himself to the rarefied world of royal engagements.Telegraph Group Ltd