Buckingham Palace
Buckingham Palace has said Margaret Rhodes's death was a private matter iStock

Queen Elizabeth's first cousin and close friend, Margaret Rhodes, passed away aged 91 on Friday 25 November, Buckingham Palace has confirmed. Reports indicate that over the past few weeks, as Rhodes fell ill, the Queen was a regular visitor to her side.

An official statement will not be issued because it was a private matter, the palace said, adding that the Queen had sent her condolences to the family. Rhodes, who was often referred to by the Queen Mother as her "third daughter", was a year older than Queen Elizabeth II.

A royal insider told the Sunday Express: "The Queen will be devastated to have lost her best friend.

"She grew up with Mrs Rhodes and they had so much shared history. They remained close throughout the Queen's reign and Her Majesty continued to be a regular visitor at Mrs Rhodes's Windsor home until very recently.

"One of the disadvantages of the Queen having such a long life is that she has had to say goodbye to so many dear friends and relatives. It is such a sad loss for Her Majesty, Mrs Rhodes's family and everyone in the royal household. She was an extraordinary woman."

Speaking to the BBC in April this year, in the run-up to Queen's 90th birthday celebrations at Windsor Castle, Rhodes asserted the current monarch would never abdicate as long as she was healthy and able to fulfil the role. "Her total dedication is something we should all be grateful for," she said.

In the candid interview, Rhodes added: "I think that should something such as Alzheimer's or a stroke or something intervenes, which god forbid, that would obviously open up a wholly lot of different circumstances, perhaps making Prince Charles Regent or something. But those are exceptional circumstances and so far she's shown no sign of wilting in the job."

It is believed that Rhodes and the Queen remained very close over the years and would have tea every Sunday after attending a church service. During the Second World War, Rhodes lived at Windsor Castle and Buckingham Palace and worked as a secretary for MI6.

In a memorable interview from 2013, when asked if she was excited about the imminent birth of Prince George, Rhodes responded: Well, you know, everybody has babies. And it's lovely, but I don't get wildly excited about it." Rhodes is survived by two sons Simon and Michael including two daughters, Victoria and Annabel.